New chicks to the flock

[areandare]

Hello, I have 5 misc hens 6 months old and 1 roo same age that grew up together. I recently received 2 cochin chicks about 6 weeks old now and was wondering when i could place them in the same coop. The coop and run are plenty big, plus the older ones free range during the day. The roo doesnt seem to care for them all that much . Should I just put them in one night with a smaller box to run and hide just in case?Also the older ones are eating layer pellets do I need to feed them seperatly somehow?
Thanks