I am a person with MS, and heat is definitely a trigger for flare ups for me. The last time we were in the parks was June of 2017, and I took Mission cooling cloths with us, and they helped a ton. I got them at Target for about $14.99, and I wet them down and placed them in ziploc bags. When I found myself getting hot, I would take a wet cloth out of the ziploc, give it a twist, and wrap it around my neck. Instant cooling! All I needed to do was re wet them, twist them again, and instant coolness again!
I move from air conditioned spot to air conditioned spot, when necessary, and I take dips in the resort pool. I'm always grateful for air conditioned busses to cool off and get a little rest, too.
Enjoy your trip...I hope you have a magical time!