I swear I tagged Washington...still not sure why it got tagged in Connecticut.

When?

Lots of web entries for the following places - let your mouse do the walking as you shorten the list...

Pike Place Market;

Experience Music Project and Science Fiction Museum - "interesting" Frank Gehry blob under the Space Needle;

New central library - winner of architectural praise and some user scorn...

Pioneer Square - one of the largest national historic districts in the US;

Museum of Flight - second only to the Smithsonian A&S in scope/size;

Boeing tour and Future of Flight exhibit - see the big jets (including the 787) being assembled in the biggest building in the world (So. Everett, around 1/2 hr. from Seattle)

Seattle Art Museum Sculpture Garden, on the central waterfront;

Museum of Glass, Tacoma, and adjacent Chihuly Bridge of Glass;

Mariners game at Safeco Field and/or Seattle Sounders FC MLS game at neighboring Qwest Field;

Ferry ride to Bainbridge or Bremerton from downtown Seattle terminal;

Visit the Chittenden Locks on the Lake Washington Ship Canal, with neighboring underwater viewing of returning salmon using the ladders;

University of Washington - beautiful campus and some interesting buildings;

Fishermen's Terminal, home port for the west coast's largest fishing fleet, also with a pretty good restaurant, Chinook's (teen and parent friendly);

The Fremont Troll, Lenin's Statue and other joys of the Center of the Universe;

Rent a canoe and paddle around the Washington Park Arboretum and Lake Washington bayous (near the U of W)

Houseboat jungles on Lake Union and Portage Bay;

Float plane sightseeing trip or day trip to Victoria - www.kenmoreair.com;

The list goes on...

Sorry I forgot about when. We're going mid-June

Do you and your son like to eat?

I just got back from Seattle a few weeks ago and I went on 2 tours from Savor Seattle (http://www.savorseattletours.com/pages/3-Home)

I went on the Downtown Tour and the Pike Place Highlight Tour. They were both excellent! I can't recommend them enough ...
This is what I wrote on Yelp:

I did both the Pike Mrkt and the Downtown Tours. (I got a discount for booking 2) IT WAS AWESOME! First let me say that the best part of these tours is that you don't have to worry about being right next to your guide the whole time so that you can hear. They have a mic - you get an earpiece!! If you have ever been on a tour of any kind, you know how exciting this is!!
Not only do you get to taste a lot of different types of food (and we are not talking supermarket size samples here either!) they are all delicious and expertly thought out. (I mean to say, they really take you to the best places ... just not to the places with the "big names") I was quite full afterwords, and I am a good eater.
I HIGHLY recommend taking a Savor Seattle tour! (or all of them) When I go back to Seattle, I am definitely going on the 2 new tours that they added!! It was worth every penny!!! (Especially since you get a discount card for all the places you visited good for 10 days!!)

Wallace - we love food tours! It just escaped mind when I had written the op. Those sound great!

Glad to help! I know you and your son will enjoy your tour!

The city seems well covered but the food tours reminded me of the tour at Theo Chocolates. It's in Fremont, and books in advance. I've yet to do it myself but have heard good things from friends. They roast and fully process their cocoa beans in house.

Rent a kayak on Lake Union (Northwest Outdoor Center has them for something like $20/hr). Take the water taxi over to West Seattle (the REAL center of the universe) and hit Alki Beach and/or Lincoln Park. Browse the stalls at the Market and take a picnic to Victor Steinbrueck park and enjoy the view across the bay and over to the Olympics. Be warned that park is frequently full of colorful characters.

keb,

I did the Theo tour too. For someone like me who just wanted a very laid back trip it was well worth the $6 ... but I wouldn't recommend it as a "must do" for someone like Trekker who will have more than enough to do as it is.

For chocolate lovers though, the factory is awesome. Even if you don't take the tour, they have samples of all their bars available and you can just help yourself. YUM!YUM! (The curry coconut is so good!)

Has anyone tried the Tillicum Village tour through Argosy Cruises? It seems interesting and unique, but I think it's new. I would love to read reviews from others.

Take the ferry out to the Orcas Islands. At Friday Harbor you can rent scooters and ride around the island. It's a full day trip, but beautiful scenery, relaxing but tons of fun. Look for jelly fish in the water at the pier at Friday Harbor.