Being in Orlando in August is like being locked into a sauna from about 8AM to 7PM. It is incredibly hot and very humid. Even with a GAC that lets you consistently use the FP line, there is walking to the bus stop, waiting at the bus stop, walking from the bus stop to the park entrance, waiting to get through security and the ticket gates, and walking to the attractions. If you're bringing a car, there's waiting for a tram, walking to the tram, etc, as well. It's just sooooo hot at that time of year, I think your daughter will be miserable given her condition!