How much protein are you thinking about feeding the chickens? I once allowed a baby chick to grow up with poults and I fed him 30 % protein. It didn't kill him but he was about the size of the turkeys when he grew up.
Chickens really don't need that high protein feed. I would think no more than 20% is ok for the chickens while the poults really need more protein for a better looking and meatier bird.
Well as far as nesting/raising........My turkeys nest wherever they decide and if the location is not safe for new poults, I remove the poults from the mom when they are hatched and bring them inside. For those that are good girls and lay eggs in the breeding pens, it makes it easier because I leave the poults with the mom. But I am very skeptical about both chickens and turkeys nesting and raising babies in the same area. A broody turkey and a new mom turkey is a dangerous pill to swallow. If it were me, I wouldn't house them together.
Hopefully others will come along and offer more than I have.