Mid July: 1 week with wife and kid - what should we prioritize?

Have you ever heard of Sauvie Island? It is the largest fresh water island in the U.S. located 15 min. east of downtown Portland. Cross the bridge onto the Island and you have entered a beautiful paradise, filled with berry picking organic farms, green space preserves with fields of sunflowers for the migratory birds to feed on, the best sturgeon fishing spots around, picnicking galore and best of all a gorgeous family friendly beach along the Willamette River (be sure to stop at the first couple beaches you come to because the beaches further down toward the end are clothing optional and are clearly signed).  There is a wonderful campground called Island Cove R.V. park that is super friendly and has fire pits for this starry nights.  In the morning there is a cafe next door to get coffee and sun yourself on the patio.  This is a very popular day trip for many Portlanders who ride bikes and enjoy the weekends there, so I would recommend the weekdays if you want to avoid the crowds.  Have fun!

Also definitely go to Troutdale and McMenamins Brewery.  You can stay the night there at this old historic orphanage turned into a grand hotel.  Filled with 3 restaurants a movie theatre, wine bar, golf course, bands on the week ends, and a spa with outdoor heated pool for guests only.  The hotel is so cheap, dormitory beds start at $30 and rooms are $50 or 60.  Great food, great beer and away from the hustle and bustle. Close to the airport BTW, so makes the perfect night before or after flying out. Just a short taxi ride. You will love it!  Go to their website first of course.  I could offer other suggestions just ask.  Native Oregonian here.  :)

If you're going to Mt Hood (Oregon) anyway, plan on heading from Mt. Hood back to Portland via Hood River and do the Fruit Loop: many stops for pick your own fruit (likely cherries in July). It's gorgeous as well as a fun activity.

I would say you definitely need to go to the Portland Zoo! Then I would suggest Oregon Museum of Science & Industry which is a hands on science center. Then if you don't mind a little drive I would suggest making the trip to Multnomah Falls. It is seriously so beautiful! Another option is doing a jet boat tour of the Willamette River. These tours are so fun! And usually they can accomadate for whatever weather there is. There are a couple food places I would suggest trying to hit while you're there also. Voodoo Doughnuts is known for their crazy doughnuts and have been featured on food network for it. I would suggest going to the location that isn't in downtown! That one is the original shop and so there is usually a pretty long wait. Also I would suggest going to Salt & Straw. They make all of their own ice cream and they have some pretty unique ice cream flavors that are pretty out there. (They also have some pretty normal flavors too). I would also suggest checking out some of the food trucks. They are located all over Portland and have really good food. They can be looked up online. Usually multiple trucks will set up in one location so there is more selection. I hope you enjoy Portland!

Portland Zoo is lovely (they have a polar bear!)

and since you will be nearby, I'd suggest you stop at the Rose Garden(it's free!)

I also love very very much the Japanese Gardens just a 5 min walk from the Rose Garden :)

Portland is definitely a very "21+ friendly" city. That said, there are plenty of family friendly attractions worth seeing. 

The thing about Portland is, a lot of our sights are nature-centered. We have a lovely Portland Zoo that I highly recommend, a beautiful rose garden, and what seems like thousands of wonderful parks. If your family is into hiking, or walking trails, I would suggest places like Forest Park, Mt Tabor, or even Powell Butte Nature Park. If you do end up at the Zoo, Washington Park would be a wonderful place to take your daughter - awesome playground - and the children's museum directly across from the Zoo is a place I have fond memories of from my childhood. The rose garden is also located in that area.
Aside from that, we have what every other city does. Movie theaters, roller rinks - I recommend Oaks Amusement Park which is also a small fair-like "theme park" - and museums - aside from the children's museum previously mentioned, OMSI is our museum of science and industry, and is a wonderful place for the entire family, hosting tons of exciting and interactive exhibits, as well as a planetarium. 
A common tourist stop here is Voodoo Doughnuts, which offers silly doughnuts - think a pixie stick, cereal, or cookie covered doughnut - that have become quite "talked about" around here. Depending on your kids sugar intake, it could be a fun stop. 

Brewery wise, most that double as restaurants downtown will be open to the entire family. Some are a bit more spectacular than others, but depending on what you're looking for, I would consult Yelp - taking into account what food, beer, and atmosphere you're looking for, that'll probably give you a more direct answer. Oregon is home to Mcmenamins which has taken several "historical" properties around our state - tons in the Portland area - and has renovated them, adding in a restaurant, brewery, and the occasional hotel. They're family friendly, really neat to look at, provide a unique atmosphere, and while the food isn't "spectacular" it's tasty, and the beer is great. They're easy to find, and they're a great choice for a simple family outing.

I hope you enjoy your trip!

Ruby Jewel Scoops or Ruby Jewel Scoops for some of the best ice cream in the world.

The Oregon Museum of Science & Industry is very kid-friendly - and you can tour a submarine there, too. I'm not sure if your 6-year-old is big enough for Tree to Tree Adventure Park, but it's worth looking into. For trying some great beer, Green Dragon Bistro and Pub will have a lot of regional craft beer. If you want  to get a bit further away, I think even a 6-year-old could handle a hike at the Ape Cave near Mount Saint Helens. Here's a blog post about it. I definitely saw some kids in there. They probably needed a hand in a few places, but most of it should be ok.

If you're a coffee drinker, there's a lot of great stuff to be found. Stumptown Coffee Roasters makes a great cappuccino, but I also recommend trying their nitrogen-charged iced coffee. The flavor of coffee, the texture of Guinness (not a great beer by any means, but the texture is awesome). Oh, and I highly recommend a stop at Lardo for sandwiches.

Have you ever heard of Sauvies Island?  It is the largest fresh water island in the U.S. located 15 min. east of downtown Portland.  Cross the bridge onto the Island and you have entered a beautific paradise, filled with berry picking organic farms, green space preserves with fields of sunflowers for the migratory birds to feed on, the best sturgeon fishing spots around, picnicking galore and best of all a gorgeous family friendly beach along the Willamette River (be sure to stop at the first couple beaches you come to because the beaches further down toward the end are clothing optional and are clearly signed).  There is a wonderful campground called Island Cove R.V. park that is super friendly and has fire pits for this starry nights.  In the morning there is a cafe next door to get coffee and sun yourself on the patio.  This is a very popular day trip for many Portlanders who ride bikes and enjoy the weekends there, so I would recommend the weekdays if you want to avoid the crowds.  Have fun!

Columbia River Gorge National Scenic Area for waterfalls- Horsetail Falls where kids can play in the water at the base of the falls. Watching the fish ladder at Bonneville Dam. A ride on the Sternwheeler Dr on the Columbia from Cascade Locks-a real paddle wheeler.

The Portland Saturday Market, Powell's City of Books and I haven't done it yet, but Glowing Greens glow in the dark mini-golf sounds kid-friendly and fun!

Also, consider a day trip to the scenic Cannon Beach (pretty much the closest beach to PDX).  This is one of the most gorgeous beaches in all of Oregon, and there is some great hiking, agate hunting in the area.    

Most brewpubs are relatively kid-friendly during the day, but they won't have places for the kids to play or anything (in my experience). As long as your 6-year-old is content to sit at the table with you, you'll be fine. Stay out of the bar sections, though! I don't have any good suggestions on specific breweries, sadly.

You might like the Portland Children's Museum or Oregon Museum of Science & Industry. I'm a huge fan of OMSI, even as an adult! It's super fun, and very hands-on. The Gravitram outside of the planetarium there is amazing to sit and watch.