This is one of the lists from last year of what was open for Thanksgiving dinner in Seattle. I like ART and BluuWater and both are downtown.
For a really nice Thanksgiving dinner you can dine at the Georgian in the Fairmont. It has a combo buffet - plated meal. Nice starters and desserts on the boards and then a plated meal.
"Any restaurants in the Seattle downtown area that are worth checking out?"
Many downtown restaurants are worth checking out, but as Lauren points out, you'll need to do some research to find restaurants outside of hotels that serve on Thanksgiving day.
Here's a list (not all are downtown) that should serve as a useful starting point:
Even though I live here, my husband and I used to spend Thanksgiving weekend at the Fairmont. If you get a room facing University, you can watch the Thanksgiving parade go right by. And if you get a room on the west end of that side, you can also see the Bon star when it's lit up.
Thanksgiving dinner was a tough one because most places were closed. We ended up choosing a hotel restaurant with the best looking menu.