Hi Mr Ed! Typhoon Lagoon will be closed for rehab during your stay, but Blizzard Beach will be open. Beginning December 29, Blizzard Beach will close and Typhoon Lagoon will open back up. Maybe that's where the conflciting information came from.
The water parks are all heated and you can swim in December if you're so inclined. Just remember if it's cold outside that it will be very cold when you get out of the water to stand in lines or walk to a different section of the park. Me, I'm a big cold weather chicken and don't leave my house when it gets below 60. I can't imagine swimming if it's below about 85, but I'm sure my kids would hop right in! LOL!