Is there anything that I "must do" while in the area? Unless Vancouver can be traveled to w/out a passport... That will be out if the question for me.
As someone mention, the Arlington Fly-In is that weekend. Can do that in probably a half-day.
http://www.arlingtonflyin.org/
Paul Allen's Flying Heritage Museum is on Paine Field in Everett, a few miles north of Seattle and just a few minutes from Arlington.
http://www.flyingheritage.com/
Boeing runs its factory tours out of its Future of Flight facility, also on Paine Field.
http://www.boeing.com/boeing/commercial/tours/index.page
Of course, the Museum of Flight at Boeing Field (south edge of Seattle) has a lot of good stuff, including a full-scale Shuttle Trainer and the former Champlain Fighter Museum.
http://www.museumofflight.org/
Pure non-aviation "Touristy" things would include the Space Needle, the Public Market, the Seattle Aquarium, and the Science Fiction Museum and Experience Music Project, a rock-and-roll museum.
The Needle, the SF museum, and the EMP are at Seattle Center which is the former Worlds Fair site. The Monorail dating from the Fair is still in operation, and you can get to the Center from downtown in just ten minutes.
The Public Market is just a few minutes' walk from the Monorail terminal downtown. From there, you can take a tallish bit of stairs down to the waterfront area, where the Aquarium is located.
Other things locally is Lake Union, a mile or two North of the Center... its the terminal for Kenmore Air's floatplane airline, and you see them flying a lot. The Museum of History and Industry just moved to an old Navy armory located on the south end.
http://www.mohai.org/
..and the Center for Wooden Boats is located nearby. There are several good restaurants along the lake, with good views of the water activity (including the floatplanes taking off).
For pure, kischy tourist things, try the Duck Tours (they tour downtown, then go on Lake Union) and the People's Republic of Freemont - lots of interesting statuary, including a troll under a bridge and a 16' tall statue of Lenin (brought back from Czechoslovakia).
http://en.wikipedia.org/wiki/Statue_of_Lenin,_Seattle
You're too late for the nude bicycling, though.
Ron Wanttaja