Even at 74 now I still love Disneyworld. We have been 5 times since 2004 on family trips (us, our kids, our grandkids, and my son's in-laws). But not in summer. We have always gone around Thanksgiving due to school holidays and even then some days were quite warm to even being hot if no wind. Can't even imagine being there in summer. Especially if kids are still very young.
Parking is actually $25 per day, but you can leave and return or even leave one park and go to another park on that same $25 parking pass.
(disclosure: we did not take the RV as that would have taken us 2 long days to get there and 2 to get back).