These are good ideas, Museum of flight is very good. As far as the underground tour, I did it about 10 years ago and it was very overrated at that time in my opinion. Just a lot of dirt and debris. I don't know if it has gotten any better.

The ferry ride is a nice idea. You can just walk on in Seattle, I forget the fare, and you can just stay on at the other end and come back. You could go to Bainbridge or Bremerton. http://www.wsdot.wa.gov/ferries/

The ferry to the islands is very nice, even better scenery, but only leaves from Anacortes which is some distance from Seattle, but worth it if you have the time.

The original REI store is gone but they have the "new" flagship store. So if you like high prices and bad service definitely go there.

Down the street from Pike Place Market is the Seattle Art Museum if you go for that sort of thing.

And if you like wine, we have about 20 wineries out here in Woodinville.

Mike

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1998 C230 330,000 miles (currently dead of second failed EIS, yours will fail too, turning you into the dealer's personal human cash machine)
1988 F150 144,000 miles (leaks all the colors of the rainbow)
Previous stars: 1981 Brava 210,000 miles, 1978 128 150,000 miles, 1977 B200 Van 175,000 miles, 1972 Vega (great, if rusty, car), 1972 Celica, 1986.5 Supra