I have one layer and eight 9+ week old chicks. I house them all together but keep their food separate. I do this by mounting the layers food higher than the little ones can reach, but low enough she can easily get in to the food. The chick food is hidden behind my storage cans where they can easily reach it but she can't squeeze in there. I figure when they are tall enough to reach the layer food, they will be about the right age to eat it. It works for us...at least for now.
Do you worry that the hens will scatter the layer feed on the ground and the younger birds will eat that? I would worry since the calcium is bad for them. ,,,