We went last January & had weather in upper 70s & low 80s during the day, but once the sun went down it cooled off. We ended up wearing shorts during the day (definitely hot enough) & then in the evening I brought long pants for myself & the kids, as well as a light jacket. DH only wore shorts, but I think he did wear his windbreaker at night.
We use a stroller so we had storage room for the backpack with clothes. Otherwise, I would rent a locker. Well worth the few $$ to keep comfortable & not travel back to the resort to change.
Hope that helps. Have fun.

Mickey & Minnie Mom