I've only been to Seattle once, but here are some things from my trip in no particular order...
ACTIVITIES:
Bainbridge Island - for calmer relaxing day/afternoon. You can take the ferry over from the mainland area. It's a drive-on ferry in case you wanted to bring a car. The ferry ride itself is a nice ride.
If you have free time and wanted a more leisurely activity, walking/biking over to Myrtle Edwards Park would be nice. At the closest point you would also go through Olympic Structure park (which is up the hill above it).
The myrtle edwards park is a long stretch along the water----people run/walk/hang on the grass, etc almost like a combo of running on riverside park in the Upper West Side of NYC (but not as grandiose).
*my hotel let guests check out bikes for free use so you could check if yours does that and take ride along the water
Savory Walking Food Tour of Pikes Market - you could say it's a fairly touristy thing to do, but I enjoyed it. Depending on whether you did early or late tour you stop at slightly different spots but it was a nice way to get a taste of a bunch of places. If you plan on buying things from the market, you also get a discount card (i think 15-20% off?) that you can use for any of the shops there during your trip (you get the card when you finish the tour).
http://www.savorseattletours.com/tours/pikeplacemarket/
Sounders game - They play in the Seahawks stadium. They have pretty great fans so it's a nice energy for a match.
Went Salmon fishing - fished for salmon. The water is pretty calm so didnt have to worry about any sea sickness issues. Depending on the season you can get different kinds. There are spots around town that will package up your catch and ship it home for you (including the main fish place in Pikes market). Some places can prepare some of it for you as well---smoked, turned into jerkey, etc.
Center for Wooden Boats - On Sundays you can go there and sign up for a FREE boat right (they usually last 45 min to an hour depending on the boat). You get there early and wait in line. Once they open the line goes inside to sign up for whichever boat they want to go on (each boat holds different amounts of people from 1or2 to 8-10-ish). The boat captains that are part of the center are the ones who volunteer to take out all the boats so you don't need to know anything. The area that this happens in shares the water with one of the sea plane landing areas so while you're out on the water you might see the sea planes taking off or landing in the water.
https://cwb.org/events/cast-off/
Mt Rainier - didnt make it there, but looks amazing. If you're in Seattle plan for a full day trip including travel.
FOOD:
Oyster happy hour at Elliott's Oyster House - nice weekday afternoon treat---sitting outside on the pier. starts at 3pm and price goes up slightly as the day goes on.
http://www.elliottsoysterhouse.com/menus/happy-hour/
RN74 - Had some good appetizers there
Salumi - Amazing sandwich shop (from Mario Batali's dad). It's a small place and often has lines (including before they open). They are known for their cured meats. Certain sandwiches have the potential to sell out.
Salty's on Alki Beach - all you can eat buffet (including oysters). It was very tasty...if you're into all you can eat buffet style. You can take the water taxi over (or a car) to that area. The restaurant is right on the water with nice views.
Pike Place Chowder - might have to try it. It was good. The lines can be crazy! If you really just wanted to say you tried it, this place is one of the stops on the food walk tour so you get a taste during that tour.