If you do go in August, I would suggest you go as late in the month as possible. We went last August from the 13th to the 18th. I knew it would be hot, but thought it would not be that crowded. Reading the boards, most people said that the crowds would not be so bad, with a lot of the southern states already having the kids start school. Well, it was hot, and really crowded. I don't mind walking in the heat, but standing in line for rides for an hour was not fun. And many times, fast passes were gone at the top rides by 1 or 2 pm, so we didn't have a choice but wait if we wanted to do the rides.
Now, we just returned yesterday from a 4 night stay at Beach Club. We left the kids home, and had a "second honeymoon". It was fantastic!! We literally walked right onto rides with no wait, including Soarin, Tower of Terror, Rockin Roller Coaster and most everything else. The only wait we had was 30 minutes one night at Thunder Mountain Railroad, but I think this was because Splash Mountain was closed, so every came on the only other ride in the area.
I never thought I would take my daughter out of school for a Disney trip, but can't pass up the chance to do this again. We are already planning another visit for next January or February! Our son will be in college, so we don't need to worry about him. You would be surprised at how many people that we talked with down there had taken their kids out of school. They said they just spoke with the teachers and brought some of their work with them to do while on vacation.
I hear that September is a lot less crowded also, and you would still have the warm weather to enjoy the pools. Of course, there is always the chance of a hurricane, but that can happen in August, too.
Good luck and happy planning!!!
Debbie