I love going in the summer. I went once the week leading to Easter and Mother's Day w/e and I thought those were worse then summer.
My tips are to go early. If a park is open early that day go to that park. Leave at lunch time, either et lunch in the park or leave and et at your resort.
Take a break-either swim, nap, do laundry, etc....
Shower again..ok that is what we do since we are sticky from the am sun/heat.
Go back to the park til it closes. I have done that with a 15 mo old, a 22 mo old and a 28 mo old. They all took naps during our mid day break. When my oldest was 7 she even took a nap. There were no tired meltdowns from my kids at 9/10 pm.
We do not do a park every day. We do a maximum of 2 days in a row of a park (ok occasionally there is a 3 day stretch) but we take a no day park to hang by the pool and sleep in until 7!
Every ride has a/c so it's not like you will be sweltering for long in an outdoor line.
We wear hats and do t forget to sunscreen ears.
We bring water, ok last time we caved and drank soda because I kept telling myself that fl water isn't that bad. This year we are shipping water. We get frozen drinks/treats.
There are the sprinkler/miter things all over, go get wet with your kids.
When we had the stroller, I would put ice cubed down on the stroller tray for my kids to suck on and play with, aka keep cool.
I only bring about 6 outfits per person because I do laundry every day. We wear 2 per day.
We have cheap mister fans from Walmart. I don't know if I am going to bring them. I may just bring one, not sure.
My kids are a bit older so there will be no stroller so they each have a cinch sack and will carry their water which will be in the thermos water bottles they have.
People always say how can you go to fl in the summer?
Well I live in ct, it gets 100*, it gets oppressive/super humid. When I am home I am either rot the beach, in the pool or inside the a/c house. Well in Disney, I am either in the pool, my a/c room or walking to a ride that has a/c.