It got so hot in August that the windshield on our van cracked - and not just a little ding that you can tape/ignore until you get home, but a 15" curved line across the passenger side.
I agree that a car in August, left sitting in a parking lot all day is very uncomfortable, nearly dangerous. Waiting for the buses was much cooler, because we made sure to get a frozen treat to lick/slurp on the way out. It was a bit messy, but nothing a swim in the resort pool couldn't clean up (with appropriate wiping of the mess first with napkins).
The resorts with the best dining are on the monorail or a nice stroll through the International Gateway at EPCOT. It is possible to do the restaurants that way, with some planning/scheduling.