I realize this is after-the-fact at this point, but wanted to share my opinion having now done Magic Kingdom on Christmas Day...
If you're going to go...GO EARLY...we were there at 6:30 for a 7am opening. Long story short, we had all of Fantasyland, Liberty Square, Adventureland and Frontierland done by about 10:15. At that point, we started walking toward MainStreet and it was like a flood gate at open. I swear up to that point, you'd never have known it was Christmas Day. It was INSANE in that area. We had only planned on spending a short time there anyway because we were driving down to my parents house. As we left, we saw busloads...and I mean BUSLOADS (the big DisneyCruise/Magical Express) buses of people being dropped off...LINES of cars waiting to get in. Jaw dropping to say the least. Now, to each his own, but I would NEVER have gotten there at that time. Unless you're just going for ambience and parade, it just doesn't make sense to me to have to deal with that many people in one place at one time. So...would I do MK again on Christmas Day? Sure I would...but you can also bet that I"ll be amongst the first in line so that my stress level stays in the Christmas spirit. Happy new Year all!
Dawn McG