If I were you, I would just plan on it being really crowded and really really hot. And then plan my days around that. It seems like getting to the parks EARLY and using Fast Pass is the way to go. And then leaving around 11am or noon, to go back to the hotel and swim, and then going back to the parks after dinner.
You might want to check out Tour Guide Mike's website. You can get a step by step plan for the parks which seems to reduce wait times in lines considerably.
Good Luck!!!!!!!