Dates? Because weather plays into things also the amount of time you have. Also, it's Pike Place Market, the street it's on is Pike St. Surest way to be known as a tourist is to call it Pike's Place
Use the monorail to get from Westlake Center to Seattle Center where the Space Needle is, Chihuly (blah but I think he's way overdone and overhyped here) and MoPop (formerly Experience Music Project) which is on my list of things to do. I went to a free concert there years back and wandered around a bit but haven't actually been there.
I think the Museum of Flight is awesome if you are into planes and space travel. They have free docent tours as well which can be a better way to see a museum, less reading and more stories. I recommend this for any of the Smithsonian museums as a side note.
The falls are good but it's going to depend on when, and the amount of rain we've had. It's the dry season (shh...we don't really have one of those) and there's probably not much going over compared to spring with the snow melt or during/after a huge rain storm. But it's still good to see but if time is an issue.
The Underground Seattle tour is great! It starts in Pioneer Square, which I think is a bit of a mess with the streetcar line construction but everything is still open. It's cool because it shows parts of old Seattle that's now underground. The aquarium is also great, though I'm biased because I spent a summer there as a high school naturalist volunteering. You do want to wander the waterfront and for sure go to Ye Olde Curiosity Shop, it's full of all kinds of odd things. Ivars is good for quick food but there are better seafood places if you want sit down.
The Ballard Locks (Chittenden Locks) are fun. You can watch the boats go between the sound and the lake and if it's fall the salmon will be going up the ladder to get to the river. Or you may see the sea lions eating them. Another place I've heard good things about is the observation level of the
Columbia Tower it's taller than the Space Needle and you can see the needle from it. It's the stop of an office building.
I recommend Dick's Drive In, either the sit in location on Queen Anne which isn't far from Seattle Center or one of the drive in locations, that you can walk up to, there's one on Capital Hill which is also a fun neighborhood to wander in. You don't want to be driving, except to get to the falls for if you want to go down to Mt. Rainier. Another thing that's fun it to take a ferry ride, even if you walk on and only get off on the other end and get back on. But that becomes a time thing too. West Seattle/Alki Beach has great views of Seattle but you would want to drive there.
The Hyatt is in a good spot to walk to a lot of things. Along with the monorail that only goes between the two stops, there's also a light rail that you can take to/from the airport or use to get between things downtown, like down to Pioneer Square to the tour, which is about the only reason I would go there.
Tip to get to the water front from the market. There's a parking garage attached to the market, if you go in the main entrance to the right of the flying fish people towards the fresh flowers and veggies there should be a parking sign that points to a hallway. Down the hallway is the elevator to the garage. Take the elevator to the bottom and you'll be at the waterfront level. Otherwise you'll be going up/down a ton of stairs.
Let me know if you have any other questions or things your interested in.