Our coop is 10 degrees cooler then outside without the fan. It gets over 100 and can be mid 90's for weeks with high humidity. I've a special place for them in our basement on the really hot days. We are installing either a ceiling fan or a big metal fan before the summers heat to avoid bringing them inside. Lucky enough, it's only hot 2-3 months out of the year. We installed a heater and wrapped the coop in plastic for the winter as it gets -20F or colder. We have a wireless thermometer to keep an eye on the inside temp. We now have good shading on our run with a roof and side panels.
I've made diapers before with my sewing machine. I was going to use them in case of an emergency. My darn dog chewed them all up. I had them lined with plastic. My hens hated it, so start them young on diapers. Opening the door will bring in a nice breeze. The super hot days, feed them watermelon and freeze a few gallon jugs of water(don't fill to the top for expansion room) and set it in the coop or run. If I keep my big garage door closed, it keeps it cooler as well. They will get use to sprinklers too and will walk in the cool water. I will put my roasting pan out in the run with ice water for them to cool their feet.
You'll learn from your own experiences. Good luck re homing the ones you can't keep. That's the hardest part. I'd never be able to do that. I think I might have a rooster and there will be no way I'd ever be able to give that chick up. We are allowed boys, but my hubby said no way would he want a crowing boy around.