You're right that Christmas is perhaps the best time to see Disney, but I'd recommend the BEGINNING of December, not the end!

Anyway, which resort did you choose? That will help with restaurant recommendations.

As for popular attractions, you can pretty much count on the fact that if Disney bothered to FastPass it, it's popular. At the Magic Kingdom, you'll want to get them for Splash Mountain, Big Thunder Mountain, the Jungle Cruise, the Haunted Mansion, Space Mountain, Buzz Lightyear's Space Ranger Spin, and The Adventures of Winnie the Pooh. At the Animal Kingdom, get them for the Kilimanjaro Safari, Dinosaur, and the Kali River Rapids. I might even be forgetting a couple--just grab a FastPass when you see an attraction that offers it that has a long stand-by line, and then take some time doing something else.