Our family always travels to WDW in June/July due to school for the kids, but it has never been a problem. We love the fact that the park hours are long, and while the crowds are more concentrated, with proper planning, you'll be fine. Use EE and FP, and don't forget the mid day break. We don't let the heat become a problem; we drink lots of water and use sunscreen and try to take advantage of the AC'd attractions as much as possible. Enjoy your trip. (We can't wait for ours).