The end of August won't be too bad as far as crowds, at least that's how it's been in past years. The kids here go back to school in mid-August, and there's a week in the middle of August when Disney usually transitions the theme park hours from late crowded hours to closing earlier. The end of August will still be very hot weather though, 90 and humid every day. Labor day weekend will be the exception to the crowds though, those 3 days will be very crowded, followed by a quick drop-off the next day back to low crowds (I've been there during this a couple years- Labor day Monday was very crowded, and then Tuesday no crowds.)