Aerin, you are in the right place! Lots of us love Seattle, so you'll probably get some awesome answers. With just a weekend, there are some 'must-do' things, and some 'try to do' things. Here they are:

Must Do:

1. Pike Place Market - This place is pandemonium, even during the quiet season. Expect to see men throwing fish, plenty of cool local artisans and craftsmen and local flowers and produce and... well, it's a market! My favorite place to eat at the market is Uli's Famous Sausage. Go with the currywurst, trust me.
   
2. The Seattle Gum Wall - Seattle's disgustingly awesome tourist attraction. The name says it all.
   
3. Columbia Center Sky View Observatory - Skip the Space Needle and do the observatory at Columbia Tower. You'll get the Space Needle in your photos, and great shots of downtown.
   

Try To Do:

1. The Fremont Troll - Just one of those cool, weird Seattle things. A bit outside of downtown, but definitely unique!
   
2. The Seattle Underground Tour - a fascinating tour of the 'underground' that will give you history, culture, and if you do the 'late night adults one,' a drink and some saucy info about our city!
   
3. Explore Capitol Hill Neighborhood - I'm not sure what brings you to Seattle, but this is the 'trendy' neighborhood... sorta. I mean, it's not suits and miniskirts, but you're going to find some amazing restaurants here! Try The Saint for good Mexcian food or Nacho Borracho for bad Mexican food. There's tons of places along Broadway that you can shop or eat at.
   

One More Category: If the Weather is Nice

1. Gas Works Park - Beautiful views of the city, lovely place to spend some time if the sky is blue!
   

Have a great time! Seattle is awesome!!

I will second everything that my husband has said in his answer-especially how much I love Cafe Campagne and Belle Epicurean!  I lived near Seattle during college and loved just people watching and strolling through Pike Place Market.  It is a bit touristy, but I also love the waterfront, take the Pike Place Hillclimb Walk down and stroll along the walking path.  There are fun little shops to pop into, try salt water taffy, and grab a bowl of clam chowder and an afternoon cocktail at classic Ivar's Acres of Clams.  The Seattle Aquariumis one of my favorites, and we always stop in when we are in town.  Make sure to visit the otters, they are hysterical!

We lived in Seattle for 6 years. Try this site for great fall foliage areas. 

http://redtri.com/seattle/where-to-enjoy-fall-colors-in-the-seattle-area 

If you don't mind the drive Leavenworth (Washington) is super cute and the German-theme does not wear thin on a great fall day. Do your research on Yelp for good restaurants ( or this one.. Been too many years for me to tell you). 

Mount Rainier, the Paradise side, has stunning fall leaves, and the drive, although 2 1/2 hours from downtown, is quite pleasant if you leave early enough. Go to a Top Pot for a warm donut and cup of tea or coffee and bring one for the trip!  

If you don't want to go that far Snoqualmie Falls is just over 1/2 from downtown. Has a great inn and shirt walking path and great photo areas. The inn has delicious food and I believe (check my facts) part of Twin Peaks was filmed there.  

Enjoy.

Hi Aerin!  Some great answers by Valerie!  Pike Place Market is a must.  Some other eateries around there I enjoy are Matt's in The Market and Cafe Campagne.  My wife and I love the weekend brunch and they make a mean Croque Madame and Oeufs en Muerette.  Mouth is watering...  I also think Beecher's Handmade Cheese is a must stop.  Sample some cheese and maybe try the yummy mac and cheese or grilled cheese.  Over in Madison Valley, there is a great group of restaurants and patisseries.  My favorites are Luc, Voilà! Bistrot, Belle Epicurean (killer macarons) and Inès Patisserie.  Not too far from there is a very solid Tex-Mex type place called Cactus.  Some other suggestions for things to see, or do, are a ferry to Bainbridge Island, fantastic wine tasting around Woodinville, and the Museum of Flight.  And if you're into Yoga, my sister owns a studio called Sol Yoga on Lake Washington.  Shameless plug.  ;) Enjoy your weekend with your Mother!