We usually go to Disney in the summer (because of kids and school), but the last two years, we've gone the Thursday AFTER Thanksgiving for a LONG weekend. It is our new favorite time to visit!!! Everything is so pretty, and the crowds are minimal! I would also suggest doing Candlelight Processional at Epcot. We usually do the package (if you're going to eat dinner at Epcot anyway - the price includes dinner, reserved seating for the show, as well as a 15% discount on purchases made that day at Epcot!) To me, the show is awesome! Also, try to see the Osborne Lights at MGM. Oh, and don't miss the Christmas tree at the Grand Floridian! It is absolutely beautiful!!! There's a really cute gingerbread house there too.
Enjoy your trip! We'll be there Dec 5-9!