I try and go to Disney the weekend after Thanksgiving, and stay until the first week of december, which is only a few weeks before you're going to go. I always hit a water park. Like the pools at the various resorts, the water is heated. And several years, I've wound up with a decent tan, as well! Of course, the weather around the country has been so odd this year that you never know what might happen...
As for which park to hit, kids seem to really like both Typhoon Lagoon and Blizzard Beach (although Blizzard Beach does seem, IMHO, to be a bit more adult oriented, with more thrill rides and such). But which park you actually go to may well wind up depending on the rehab schedule: One of the three water parks will definitely be closed, as they roate during the off-season, giving the parks a rehab. But no matter which water park you hit, I'd count on having a really, really great time!
Richard