My 2 cents would be to try to get a room downtown on Priceline, you should be able to snag a 4* around $125. With regards to the car, you could rent a car from one of the downtown car rentals agencies for a day, and that way avoid the very high parking fees. I know Hertz has a place in the same building as the Grand Hyatt, and I’m sure there are several others. As far a downtown being pedestrian friendly goes, Seattle is hilly, but the buses are free in the downtown ‘free ride’ area