This is our third end of August trip coming up! IT is hot, but if you keep ahead of it, meaning you don't get overheated, you'll be fine. We stop in some of the air-conditioned shops, even for five minutes, to cool down a bit. The kids have water bottle carriers and drink water frequently (hard for my son, but I keep at him!).
Bring extra bras or plan on doing lots of laundry! Nothing worse than wearing a damp sweaty bra, or having to put one back on after a shower or dip in the pool (YUCK!)
Crowd-wise we've been pleased. Sure there's people but it's not too bad. Use EMH in the morning (night EMH's were very crowded) and use Fastpass.
See you there!