Hi Tejas!
I know you are packing away right now and your household must be beyond excited for this trip happening tomorrow! It is often difficult to know what to bring when you are changing climates.
I just left
Walt Disney World and can tell you the best advice for this time of year is to think layers. During the early morning and after the sun goes down the temperatures can be quite chilly. Once the sun comes out you will want to shed all sweaters and jackets as it is warm. Bring a light weight backpack or bag that you can keep these layers in while not using during the day.
Swimming is certainly an option during the heat of the day and all pools are heated to 82 degrees. Rain is not common at this time of year so check the long range forecast for the area to know whether you think you should throw in the raincoats. You can always purchase the simple ponchos from any Disney shop if you are caught out in the rain.
Hats, good walking shoes, and sun screen are necessities no matter what time of year. The Florida sun is intense even in the winter and for guests who are coming from the north they can underestimate how strong it is. Shorts are fine with longer pants if you are planning any outside evening activities.
Hope this helps with the last minute packing thoughts. See you real soon at the house of the mouse and friends!