Just adding in some personal experience here. We have traveled to Disney 3 times in the past few years with my mom who has pretty severe MS symptoms. First, the ECV is a must and it really helped her be able to enjoy the parks. Disney is so different and it is easy to overdo yourself the first day, then be out of commission. The ECV helped us avoid that and honestly, it was easy to use around the parks and in the lines. Second- have a good touring plan. You will be able to precook 3 FP+ which is 3 lines you won't be spending massive amounts of time in. One thing we planned was making sure if we had an outdoor queue, our next attraction was indoors, nice and cool. For example, if waiting in line for Peter Pan, next attraction was mickey's philharmagic. Plan, plan, plan. We also hit the restrooms frequently, and to be honest, she wore a pad in case of any leaks. Lastly, misting fans, neck rags, and a cooling vest will work wonders in the heat. We took a small cooler bag with baggies of ice with a rag in it, we swapped out rags as needed to keep them cool. Also lots of ice water, a visor for sun, and listening to her cues as to how she was doing. We had no need for the GAC or DAS and have had great trips. Planning will get you miles farther than the DAS. Oh and get there early to beat the heat of the day, take a break then go back at night. A others have said, the worst heat and sun is not while waiting for attractions, it is while traveling from point A to point B.