We did Thanksgiving at the Fort a few years ago and enjoyed it.
The Fort will fill all during Tgiving week and be full Wednesday-Sunday just about. Theme parks are full Thursday-Saturday so if you want to do parks go in the early part of the week.
My one piece of advice is not to wait too long to do your grocery shopping for Thursday. The grocery stores got picked over when I went the day before for things like jarred turkey gravy, instant mash potatoes, etc. Had to scramble a little bit but got it worked out. I also wanted to buy a fresh turkey but couldn't find one in the stores so had to buy a frozen bird and thaw it slowly in a separate cooler (it thawed in time). We bought pumpkin and pecan pies from the grocery bakery.
It's fun to cook and eat and watch the college and pro games outside on the telly.
We had a pop up and I used a tabletop roaster oven to cook a 20# turkey and we fed 15 people (other family members stayed over at Pop Century). It's fun with a big group. You'll enjoy it.
Also try to be flexible. We had to eat outside and the day after Tgiving was better weather wise so we had the big get-together on Friday.
Take lots of pictures and share a trip report with us when you get back.
Bama ED
PS - some campers will already have some Christmas decorations up. Watch the progression each morning down around Pioneer Hall. They usually put the Christmas tree up outside in front of the Trails End porch the morning after Thanksgiving Day (Friday).