I've heard to freeze some water bottles to let them stand on when it's too hot. Or maybe put some ice cubes a few times a day in their water. I will probably get one of those clip on fans and set it by timer or thermostat, I know several people prefer to use fans of some type to help keep the chickens cool. I'm just trying to figure out how to manage the cord without compromising a secure coop. I might have to have it outside blowing in, which is fine, but that means I have to use a box fan or something bigger than I was intending.
As far as keeping them warm, I never used a heat lamp when they were a couple weeks old, but we have these heating pads we use for our seedling trays, they don't get very warm, but were enough. I may just get a heat lamp come winter anyway as I'll probably want to give them some extra day time light anyway, and again, set it on a timer. I will bring them in if the temps go below freezing, but we rarely have that cold of weather. I hear chickens tend to be more cold hardy than hot hardy, so I'm a little worried about our Texas heat.