If you are interested in having dinner and meeting other FlyerTalkers, there is a dinner ("Do") on Saturday night.

http://flyertalk.com/forum/showthread.php?t=470332

I too enjoy the Ballard Locks - I love watching the salmon swimming upstream (except that sometimes, I have 'salmon days' at work) when they are running and seeing all of the beautiful boats passing through.

I drove by the Museum of Flight in August (on my way to FedEx to pick up some flowers) and was thinking of stopping by and taking the tour either on Sunday or Monday. The Underground Tour looks interesting as well.