I just bought a mobile swamp cooler/fan for my chicken cabin, and misters for the runs, plus more shade cloth. I also give them ice in their water, freeze water in bottles for them to lay around, hose down the earth so they have cool places to dig into, keep a small "pool" of cool water for them to soak their feet in...or for me to soak their feet in if they seem overheated, and feed them frozen veggies and chilled watermelon. I'm utterly paranoid that I'll lose some of my beloved feathered friends this coming week...especially my Bielefelders, which seem to be really struggling with the heat.
Got the fan going and wetting down their run twice a day. Ice in the water which they like, but I will add frozen veggies. 5 of them are 13 weeks so not babies, I do have some silkies that are younger and I am doing the same for them. If it gets really bad I will bring then inside for the week.

Just a word of caution, I would
think allowing them to get acclimated to heat would help them. And if the are brought inside, when its real hot, I wonder if that would end up being a detriment to them, & I wonder whether or not they might feel like its a shock to their system to be in the hot weather when it's over a hundred degrees. anybody with more experience the meeting might be able to chime in. @ChuskaMtns@desertmarcy
it's just my thoughts as a pursuing medical student.
Everything else sounds wonderful that your doing!
On a side note, and it's probably just me, I'd like to be super careful and I choose not to purchase any misters at least the ones at Home Depot, due to that they had cancer causing ingredients, if you will .. in their materials. So, I'm using watered down ground areas under trees/shrubs, cool water pools of plant saucers and a baby pool for them or me to help keep them cool this summer; with frozen bottles placed in them, as I've used in the previous summer.