Don't start worryig about the weather so much that it ruins your magical trip. Nothing is more magical than being in WDW during the holiday season. I live in Miami and most times it is 80+ on christmas morning. I think the last time we had a christmas under 75 degrees was years ago. In orlando it can be beautiful and 75+ degrees in the day and be 40 at night or it can be 80+ and 70 at night or 40 in the day and 30 at night. You will never know until you go so don't let it worry you. It will be blue skys and beautiful no matter what because you are there with your family and hey look...it's Mickey in a santa hat.