When I began planing our 2014 trip to Disney I was positive we were were going in October (and I really wish we still could

). However as I spoke to the high school two of my children will be attending, pulling them out for vacation is not a possibility - they will fail them for unexcused absenses.
So I began planning for August, the two weeks before they go back to school - August 10-23. I am worried however about the heat in August during this time. We were outside yesterday for the 4th - about 4 hours in the morning (9-1) and then from 4:30-10:00 yesterday afternoon/evening. This is how we would be traveling at the parks if we keep August. By the end of the day yesterday everyone was miserable. So I am again taking a look at our travel dates.
I have to travel on schoool breaks because of the high school situation. I am looking at December 17-28. This puts at Disney during Christmas which is said to be insanely busy. The other option is the week of Thanksgiving and staying until Tuesday of the following week.
This is our first trip to Disney as a family, and probably our last big family vacation. My oldest will be in his second year of college, my daughter will be in her Sr. year of high school, my other high schooler will be a freshman, and my youngest will be first grade.
Anybody have any input that will help me settle on dates. Thank You