Just as an FYI-
I made my brother go to Magic Kingdom with me ON Christmas Day 2 years ago. We had a FANTASTIC time. However, it was SO PACKED! I did not think anyone would be there, that everyone would be at home with their families.
WRONG!! By 1pm they had closed the entrance because the park had reached capacity. It was really busy. The lines for EVERYTHING were really long.
This was just a head's-up. Again, Carl and I had a great time, the weather was GORGEOUS (I wore jeans and a light sweater, Carl was in jeans and a t-shirt). Plus, it was fun to walk down Main Street with all the decorations up and a cup of hot chocolate in my hands! Plus, they give the afternoon parade a Christmas theme (although it's NOT THE Christmas parade you see on t.v.)
I just thought I'd give fair warning about the size of the crowds. GET THERE EARLY!!