Couple of things, since we always go to Disney during Christmas...
1. Bring both warm and light clothing: The weather changes a lot during Christmas in Orlando, specially in january. One day may be very cold (40's), and the next day be on the 80's. What we usually do, is bring light clothing, jeans, and a jacket we can put over our t-shirt if it happens to be cold.
2. Start of January is your best time... At least its the way we've come to realize... We try to do all of our "out of park" stuff during the last week of december, and then hit the parks on January... We've been able to go on top rides again and again with hardly any lines...
3. Depending on your desire for crowds, you may want to avoid Christmas Eve on a park... We tried to receive the new year on MGM last year, and we decided not to do so... You could barely walk, and we got to believe that it was more painful than fun... So we left to our hotel... A friend did the same on MK, and he did mention that it didn't feel as crowded, probably because of the size.
4. Certain shows at the parks can't be missed... You must try to see Fantasmic at MGM, Wishes (or whatever firework show they have on) at Magic Kingdom, and Illuminations on Epcot.
5. If you want to enjoy most of the parks, you MUST get yourself some ponchos... These are very easy to carry on a backpack, and will save you from getting soaked on a cold day while riding Splash Mountain at MK, or Atlantis on Sea World. On a related note, it hardly ever rains during this period, but if it does, it gets pretty miserable...
6. If your kids like basketball, and you don't have a local NBA team where you live, then a game may be a good idea... I live in Puerto Rico, so every time we fly up there on Christmas try to hit the Christmas day game of the Magics...
7. Make our dining reservations on the 180 day mark, not later... It gets pretty busy at the main restaurants, and it is better to be safe than sorry...
8. Waterparks are not a crazy idea, specially if you run into a "warm" day... All the pools at the parks (at least Disney waterparks) are heated, so as long as you bring a change of clothes, you'll be fine...
9. Must try Planel Hollywood... I tell everyone that they must... Being quite honest, and being an Emeril's fan... I wasn't as impressed with the food on Emeril's (Universal), as I was with the food at Planet Hollywood (Downtown Disney)... Ribs have to be tried...
10. Other hints for parks, which apply no matter when you go:
- Before going to any park, decide on what rides you want to see the most, and go there as soon as you enter the park. For example, on MGM, Rocking Roller Coaster and Tower of Terror.
- Use your FastPass smartly. Use them on the rides you want the most.
Let us know what your experience is in visiting Disney, if any, and if you are planning to stay on or off site...
Take care, and hope this helps...
Cesar