It will still be busy as not all schools are back in session at that time but during the week shouldn't be too terribly bad. Remember...it's hurricane season then and it's still very humid so keep that mind.
We've gone to Disney twice during this same time period and though Disney is always crowded, the lines weren't too bad over there. But like Metro said it is hot and muggy--bring plenty of water and use a mister to keep cool.