We were in WDW from 7/22-8/1 and had a great time with no problems despite the heat and humidity. Here's what we did:
We also got to the parks early and went back to the resort to swim in the afternoon. On days where we didn't want to do this, we got a last minute adr at a restaurant in the park and ate an early dinner. In world showcase, we got an adr at Teppan edo for 4:30. We had a nice, light but filling dinner and were able to go back out refreshed as the sun was starting to get less intense. We were able to stay until 9 p.m. after beginning our day at 7:30 a.m.
We drank a lot of water - we brought a soft cooler and filled it with bottles of water. We had a stroller so we kept it in the bottom basket.
We had a 14 month old with us - we put a white hand towel from the hotel under her head to help with sweat. I also got a stroller fan that I HIGHLY recommend. I got it on
Amazon and it cost $10. It's a green and yellow clip on fan that lights up. I would put it on the back of the stroller (where the mesh is) when it was reclined. That way, it would blow on her head and she wouldn't grab it. It worked really well (we had to replace batteries quite often).
Tons of people asked me where I got this fan. So many people had bigger, heavier ones (like the mickey head fans) and they could see how well this worked - yet it was really lightweight. As I said, I highly recommend it.
We did have spray mister bottles. We used one here and there but not a ton. We also wore hats, sunglasses and sunbock.
My husband wore polo shirts that we found at Kohls - the moisture-wicking ones and they worked great. He is usually completely soaked from sweat but these kept him relatively dry and his shirt was never wet at all. I only bought light colors (no navy or black) and they really did the trick.
Popsicles, soft serve ice cream and just taking a break for a few minutes in a cool spot really made all the difference.
Hope everyone headed to WDW anytime soon has a great time. I didn't love the crowds of July but the heat can be very do-able if you keep hydrated and go with the flow!