I think that if you are staying at a Disney resort that you can get back into the parks even if they are at capacity. Also try to stay out of the MK; its the worse for crowds on xmas. We walked into the park one day looked down Main Street then left immediately and went to Epcot. It was so crowded it was claustraphobic.
Another idea is to eat at one of the resort restaurants. We went to Disney every year for xmas for about 11 years. After the first year we stopped going to the parks on xmas day. We would make that be our water park of hang out at the hotel day. If it was chilly we would go to DTD; Disney Quest was not open then but that's a good option too. The parks are nuts on xmas day and the restaurants are crazy; we didn't like using a day on our pass to stand in line just to walk down Main Street and have rushed or poor service in the restaurants. Most times we would make a PS at a character b-fast (we had little ones in our party) at one of the hotels.
If you have never done xmas day in the parks and feel like its something that you really want to experience they just go in with the attitude that you are there just to people watch and enjoy the mood.
