Seattle is a great town; I went to college there and never regretted it for a minute (well, maybe on day 89 in a row without sunshine... )

I recommend a day-trip to the San Juan islands. Ask any local and he or she can direct you precisely. Basically it's north on I-5 for about an hour and then west to a small town with a funny name and a ferry port.

Take the ferry across and Friday Harbor, rent a motorbike, explore the island and have a nice picnic with a special someone.