Check out the Museum of Flight in the hometown of Boeing! This museum has lots of history, and an outdoor area with larger planes that you can board including a Concorde (The real star of the Parent Trap) and Air Force One (The one JFK used!).
Check out the museum of Pop Culture, one of my (Abby's) favorite museums in Seattle! Check out exhibits featuring Jimi Hendrix, the stop motion animation sets from Portland based company Laika (See the real Coraline!), and movie props from popular Horror, Sci-Fi, and Fantasy films (Including one of the dresses from Princess Bride!).
Experience the Washington Ferry system for yourself with a ride from downtown Seattle to Bainbridge Island (Home to the wonderful Matthew and Papajani Families). You can walk straight into Winslow off the ferry to stroll the streets, grab a coffee at Pegasus Coffee House or a glass of wine at Eleven winery before walking onto the ferry back.
If you'd like to experience an alpine lake, Lake 22 is a great option! Pack a sandwich and a pair of dry clothes and enjoy a gorgeous hike with an alpine swim at the top. Parking is limited so if you're going on a weekend, try and go earlier in the morning. A Northwest Forest Pass, a National Forest Recreation Day Pass, or an America the Beautiful Pass is required to park at the trailhead. You can purchase a day pass online or at various vendors.
Entrances to Mount Rainier are timed, so try and book a time beforehand. This is an easy hike that is out and back to a fire lookout. It has great views of Mount Rainier - plus if you're lucky a mountain goat or marmot sighting! make sure you bring water and sunscreen. (Follow the Sourdough Ridge Trail NorthWest).
We did this for Brett's 29th birthday, such a fun sail around Elliott Bay. Plus it's Byob - so bring a Sweater and a Kahlua Coffee!