Congrats, FNW!! Glad to hear it.
Clams, we did Seattle-Vancouver-Victoria w/ the kids when they were about the same ages as yours are now. Great trip and I'm sure you'll love it. The famous Gardens on Victoria are of course a must - truly spectacular, but we all enjoyed the island as a whole much more than we expected to. If u have a choice, err on the side of an extra night/day there, espy if u can find a nice b&b. Vancouver is a great city. I especially remember the big public park (their version of Central Park) which had a lot of kid activities and the old or gaslight part of downtown, forget what it's called.
About halfway between Vancouver and Seattle and right off the main road between them are 2 well known touristy towns, the names of which i forget but they're in all the guidebooks (if u can't find 'em let me know and i'll figure it out). Despite the "touristy" tag, I remember them as being well worth the stop. Very picturesque and different than the east coast equivalents.
Seattle's another cool city but as i recall, not worth an extended stay. I especially remember the Science Museum beating the east coast versions (including the very good one in Boston) all to hell. All members of our & the other family we were traveling w/ had a blast. The downtown fish pier thingy is, i guess, a must visit, but unlike the 2 towns mentioned above, it's touristy in the typical & boring sense and much the same as what you'd find in most east coast cities. The Space Needle's another tourist must do, but a pretty good version of the type. If u haven't had too much of the outdoors by the time u get there, fairly close to Seattle is what i believe is the only rain forest in the continental US and not too far in the other direction is Mt. Ranier. If the schedule works out, I would try to catch a Mariners game, but i don't know if your family's as into the whole baseball/ballpark thing as mine is. When we were there, the Hendrix museum was still in the talking stages, but i think it exists now. Don't know anything about the specifics, though. I sort of remember the U Washington campus as a nice visit, but don't recall it all that well.
I don't remember any specific restaurant as a singular stand out, but the food in all locations was really excellent. We ate really well at all price points from cheap lunches on the go to fancy-ish restaurants.
Edit: Doing something on the water is a natural all along the coast there, including Seattle. We went to a wedding on Bainbridge Island, so that worked for us, but a ferry to any of the close islands makes a great day trip or, if it's your kind of thing, renting a boat for a day on the Sound would be a fun time.
(still trying to figure out the hockey love I am having)
(party planned for May) 
....hmmmpf