No, not at all! If you can go after the 1st week of August, most of the kids in Florida and many other southern states are back in school, so you may miss out on some of the local crowds. Yes, it is hot, so just plan your day around it. The parks are still open late through the 3rd week of the month, so you can go at opening, until you deem it too hot, and then return in the later afternoon and stay until close. We have been to Disney once in early August, and didn't have any problems at all. In fact, we are taking an impromtu trip this August for a couple of days.
Have a great time!