That is very wise. Likewise that is what I will be doing I got a 135 gallon stock tank that I plan on re using as a raised garden bed for Herbs in the Garden any more chicks I plan to get will be hatched under a broody.
Wow 7 dogs!? That must pretty amazing! Man I thought my TWO were handfuls haha.
Those puppy play pens are gonna be a good idea. You can line the bottom with a tarp of sorts along with their bedding. And storage totes are a rather easy setup as well. Back when I raised my first set of chicks 5 years ago and tight on space (and money

) I went to my local Walmart and picked up a clear storage tote worked just fine for me. I got 8 and two died. In fact I just saw some outdoor/indoor play pens for small animals at my Costco today along with some pretty big totes as well! Just keep in mind to have some sort of cover for the top to keep the little chicken floofs inside and safe from 7 wagging tails

unless that isn't something your worried will happen. Although wandering chicks can be a hassle if I've ever heard of one