We went Thanksgiving week a couple of years ago and loved it. It's cool in the mornings and at night but the daytime is lovely. We didn't get any rain that week, which was nice. A little too cold for pools and water rides IMO (but we're from Texas, so 70 is kind of chilly) but there is a lot of other things to do. Thanksgiving Day is pretty busy of course, but we were able to enjoy a day at MK and have a traditional Thanksgiving dinner at CRT. Many restaurants have the traditional meal for that day, so check around if you're there that day. It's usually suggested that you avoid MK on that day because it's the busiest park of the day and Epcot and AK can hold more people better so it doesn't seem as crowded. The longest lines we saw were for the monorail and of course FP for Soarin and TSMM ran out quickly. That won't be an issue with FP+ now though, so just make sure you make your reservations when you can. The holiday decorations are awesome, especially the Castle and the Osborne lights. Photographers were every 5 feet, so if you want your picture taken that's a great time to do it. We did our family Christmas pictures there that year, which was nice. They don't do
MVMCP or the Candlelight Processional that week, so if those are on your list you'll have to arrive early or stay late. There aren't any discounts that week either, so again you'll have to arrive early or stay late to try to get some kind of discount. It's not as bad as Christmas/New Years but probably on par with Spring Break.
Have fun! Maybe we'll see you there.