We were also there last year Dec. 28-Jan. 4. We were usually in slacks and light jackets for the mornings, in shorts and t-shirts during the middle of the day, and back in slacks and jackets after dark. We were swimming and sunbathing several days, and found it to be wonderful. The sun was out bright and warm, and the water was very nice (BWV clown pool).
We did have gloves and ear coverings (earmuffs, hats, hood on jacket, whatever each person chose). On the night we sat outside at Fantasmic, it was very chilly. We were nice and comfy while we saw some people blowing on their hands, hunching their ears down into their collars, etc. So I'd suggest packing gloves and something for the ears just in case.
We loved the weather that week, except for the monsoon that came through on NYE. Boy, did the rain ever come down!

But by the next day it was sunny and nice again.
When I went back down about 3 weeks later, it was freezing.

That was a short 4-night trip, and daytime temps were mostly in the 40s for our whole stay. We still had a great time.
I'll be back down this year Dec. 26-Jan. 4 and I'll be bringing my layered stuff again.
