Poultry Talk Ontario (pto.ca)

We're going to try something different when adding my 5 week old chicks to the flock.
First of all, we are going to put them in one half of the chicken run (enclosed) with 5 ISA Browns. They have kept themselves separate from the red & black sex-links. Since the ISA's are quite docile (not like my RSL's and BSL's), we're thinking it may work.
Secondly, and this is a question, What do we do about feed? They should still be on their medicated starter, but then there is the laying mash for the hens, too.

You can put them all on grower for a while - or Purina flock raiser if you can source it - and provide extra calcium free-choice for the laying hens. I have always introduced a bit slower: I leave the youngsters in a fenced off area within the run for about a week where they can all see each other but can't touch, and then I try introducing them while "free-ranging" in the yard. If that works well, then I try opening up the fence with plenty of scratch or greens or whatever to distract them, and supervise/monitor for awhile until I feel confident that there will be a minimum of disagreements. I also have a separate brooder coop within the sectioned off area, and leave it there after they've been integrated in the run, and they have access to it until they decide on their own to join the rest in the main coop. It usually takes a few days/weeks for that, and I do give them temporary separate roosting options from the main roosts, because the youngsters are not often welcomed right away.
Anyway, your way may work in your situation. Good luck!

At 5 weeks old I wouldn’t lock them in with adults yet. Some of my most docile birds are the ones I have to be careful of around chicks. Mine all mingle together in the yard but have lots of space to get away. And they have their own food and sleeping quarters until they are roughly as big as the adults. Your chicks need a place to get away that the big birds can’t get to. And they need their own food and water supply.
As for food I would switch to all flock or pullet/broiler grower. It doesn’t have the added calcium. Just provide oyster shell free choice for the layers.

Adult production hens that are actively laying, can eat medicated chick starter for a while with no problems. Just make sure they have a calcium source like oyster shell or dolomite pea gravel.

Thanks Jaye, Happy, and WWW. We ended up making an "executive decision". We moved all the adult chickens together and put the chicks in the separate half of the run. The ISA Browns are not happy and want back into their sort of "safe zone" from the other hens, but it'll have to do. This way, we can let all the adult chickens out to free range, and there is no food issue.
So, last night, most of the hens (14 - 15) jammed themselves into one coop with the rooster, and only 3 - 4 hens went into in the other coop.