This is SUCH a fun drive -- I did it last June (late June, so just about the same time as you), and really enjoyed it. I took Highway 1 -- this is the "true" PCH in California, but it connects up with the 101 through much of the upper Redwoods, and is the PCH after you cross into Oregon (and through Washington).
Here are my tips on places to stop and see in California:
- Point Reyes Lighthouse -- it's well worth the long drive out on the peninsula for this cool lighthouse. Also, Point Reyes National Seashore is just a beautiful place in general.
- Stop at Nick's Cove & Cottages for lunch or dinner -- they have amazing fresh seafood, and I believe have guest rooms for rent too.
- Stop and see the big rocks anywhere along the coast north of Bodega -- this is where you get those iconic views of the rugged coastline, an lots of twisty turny roads!
- Point Arena Lighthouse and Museum... can you tell I love lighthouses? Each one along the coast has its own unique story, and most have amazing views!
- I heard Navarro River Redwoods State Park is the iconic place to stop and enjoy the trees -- I ended up not having time, but once you start to get into northern California, there are *tons* of Redwood viewing opportunities!
- Stop and see the unique and beautiful Glass Beach in Fort Bragg. I somehow missed it, despite following the map....?
- As you turn inland, you'll join up with the 101 -- right near that junction is the Drive-Thru Tree Park.
- Once you hit the 101, you're inland for a long stretch until you hit Crescent City... be sure to stop there for a night, and perhaps see Battery Point Lighthouse if you're not tired of them yet.
I don't know the Oregon coast super well, but there are four places I know for sure to stop/see:
In Washington, things get interesting. The 101 stays along the coast until it crosses onto the Olympic Peninsula. Then it creates a loop -- it goes up over the peninsula to end back down near Olympia. So you actually have to go up and over the peninsula to follow the *full* route of the 101 and then join up with I-5 to get to Seattle.
Here are some places along the 101 that I enjoyed:
- Cape Disappointment State Park is a beautiful place to stop and stretch your legs.
- There are several places where you'll see signs for "World's Biggest __ Tree." Stop and see them -- they're amazing!!
- Ruby Beach gives you the Washington version of rugged coastline.
- Drive through Forks and laugh at how woefully inaccurate Twilight is.
- I stayed on a boat (Airbnb!) for a night in Port Angeles. It was stunning!
- Dungeness Spit is a beautiful wildlife refuge.
- Visit Port Townsend, a cute seaside lumber town.
Okay, that was a lot of suggestions. Hope this helps you choose!
Have a great trip!