We went last year Sun, Mon & Tues before Thanksgiving. It was definitely crowded! Not undoable but definitely plan on getting there early & using fast pass to it's max if you don't want to wait in long lines. I remember splash got to 90 minutes and space mountain was about the same (all days we were there).
We still had a blast though! A crowded day in Disney is better than any day at work!
We're trying the following week after Thanksgiving this year so we'll see how that goes.
Have fun!