Yup, I've already started to think about it. I've seen pictures of kids all dressed up in their princess best at the parks. Yes, it's cute. Yes, it makes for awesome pictures. But, no. It's not practical for a day running around at the parks.
So, I am planning on bringing a dress for the girls, in case they really want to dress up for a day. But, the rest of the time I'll have some Disney clothes for them. I am also planning a couple tutus & skirts to coordinate with some tops to mimic the princess look, without the big, uncomfortable dress.
Even though its Florida, it can still get cold in the winter. I know this first hand. I remember being at Epcot in 2006 wearing a sweatshirt, winter coat, scarf and still freezing. So, who knows. We'll have some options for all weather. I'm a notorious over-packer anyway, so that shouldn't be difficult for me.
I also picked up rain poncho's just in case. At least I'm fairly certain we won't need snow boots!