If you are looking for tropical weather, I would head further south in Fl., as the weather can be iffy in Dec/Jan. Sanibel Island, the Keys, Marco Island are a few places that will offer things for kids/adults. Prices will not be cheap mind you, as it is almost as expensive as Easter break.
If not worried about the weather, one year we did KSC and Sea World. It was less expensive, the kids love SW and we wish we would've alloted 2 days for Kennedy. One drawback is it is crowded as the locals are off the same time. We are in the same situation, have the time off after Christmas, but we are waiting for ExEverest to open before a return trip to WDW. a catch 22 as DH has less time in the summer, when we wish to spend at least 9/10 nights in Orlando. If we spend to do anything this Christmas when DH has off, then we will be short for our summer trip. I sure do miss the awesome room only codes...we had ASMU for $55 one trip, including tax, and CR for $134! Man, those wer the days!
Pam