I guess we are ones that don't mind cool. Day started at 62 degrees, but warmed to the mid 70's when we went on Christmas 3 years ago. You can wear a short or long wetsuit, and that definitely helps with the cool, plus, the lazy river, is like bath water warm, and we hung out there quite often. Lastly, they have heaters around you can always stand next to, that and a ton of towels around ya.
I am hoping it's unusually warm this Christmas. My kids both wanted Discovery Cove for Christmas again.
And, I hope you have a great time and great weather when you go.