We have not been in July but have been in August. It was HOT. We would go to the park in the morning. Go back for a swim when it got too hot and then go back to the parks in the evening.
When we were there in late August there was almost always a thunderstorm that closed down the pools from mid to late afternoon until early evening. Probably makes sense to schedule a sit down meal for that period.
Mid June to mid August is the summer peak so yes it will be busy. If you can go mid to late August, starts about the 16th, it is a Value period so the crowds and Room Rates are much lower. They often have 'free' dining during late August if that appeals to you. (Our preference is taking a lower room rate over 'free' dining but we have APs so we get the TIW card for the 20% discount on food & beverages. Which is a better deal depends on group size and dining and accommodation preference.)