My 6 week old jersey giants and my mystery chick are with the adults now. At 4 weeks old they were in a large parrot cage in the coop where they could see everything. At 5 weeks I put them in a brooder cage on the floor. They could see the adults, and the adults could see them. After a few days I left the cage door open during the day. They moved in and out and mingled. A couple of hens each gave one peck, but nothing significant. The rooster actually seems to protect the babies. Now The cage has been removed and repaced with a small perch under a heat lamp. When they get cold or tired they rest there. However, keep in mind that I have no mean chickens, and my rooster is exceptional.
The 6 week olds are running around the coop with the adults. The 5 week old pullets are in the brooder cage on the coop floor. Five 4 week old giants are in the parrot cage. Five 4 week old giants are in the garage. And the silkies are in a brooder cage on the coop floor. I changed the adult's feed over to Purina Flock Raiser so that everybody could eat the same feed, and the babies would get adequate protein and nutrition. I just leave oyster shell out for the hens.