I'm trying to integrate my 8 week old chicks, out of sheer necessity. We've been letting the adults and adolescents free range in the back yard at the same time for a couple weeks. Mostly they've avoided each other. There were a few pulled feathers and pecks. Nobody's gotten killed so far.
Right now, I have the chicks staying inside a Dogloo out in the chicken run. They have free range of the run and the adult chickens are locked in the coop where they can see and interact with them through the wire. (It's a Southern coop, all wire on the front to let in the breeze) This afternoon, we let all of them out in the run together and left the coop door open. The adolescents explored inside the coop and the adults had their "gobble the grass and all possible bugs" time. We fed them in two separate areas, because the adults would not share with the adolescents.
I am hoping that another week or two will find us able to move all of them into the coop together. I am, however, going to completely replace all the roosts when I do! That way the adults will be just as disoriented as the kiddoes.