I can attest to the cooling vests. I have dysautonomia & erythromalgia (among some other stuff) which make me super heat sensitive. If the temperature is over about 74 & sunny, out comes the vest. I've even worn it in the house in the dog days of summer..... or after a hot shower.......
There are several "levels" of cooling attire - from wet & evaporate to ones that pump cool water - in between are ones that hold freezer ice packs. The ones I am using is an evaporation one. I got it from
Amazon. It's made by Hyperkewl. Don't be tempted to size up because you want body contact with the vest.
The other thing that helps me alot is a very good, super insulated water bottle. I need to drink alot of ice water to keep my core temperature cool. It has to be ICE water, hence need for super insulation like a Yeti or something that states it keeps hot/cold for at least 8 hours. And a good hands -free way to carry it so you don't lose it,lol. (which I have - several times) I carry electrolyte tablets by nuun to drop in my water every other bottle. Too much water without electrolytes can really mess with many of my symptoms.
Sending you good vibes on your trip. It may be a new way of doing WDW, but you might also find alot of Silver Linings because you have no choice but to "stop & smell the roses". Some of my favorite memories are people I met & conversations I had while people watching on a park bench.