If heat is a real issue, you can try feeding early in the morning and later in the evening, but take any feed away from them during the day. It is kind of interesting how it works. A lot of heat is generated as they metabolize and digest feed. It is somewhat counter intuitive, but when I was a kid, we raised meat birds for exhibition and did this. Heat is hard on birds and while the meat birds did not grow as fast on restricted feed, they stayed alive on the worst hot and humid days.
Just keep plenty of water in front of them and shade.