I've done Thanksgiving but it was a few years ago. I remember it being busy but not awful. We also did EPCOT on Thanksgiving and it was great. We had dinner at Biergarten and it was a blast. We were with a big group and we all fit at one long table and all the kids danced. Great memories.
Exact same plan about 3 years ago. Yes, busy, but manageable. Plan your fast passes, be patient on others, and be prepared to skip crazy long lines (i.e I am NOT waiting 150 minutes for Sorrin').
One note. Thanksgiving is a blackout date for certain things. For example, If memory serves me correct, not only was Biergarten $5 more than on other days, they also do not take TiW. We had not been their on a holiday previously, and were not aware of that.
I guess that should also be noted that many restaurants in the world will offer all the food of a traditional Thanksgiving Dinner. So, you may want to verify if and what the special menu will be.