To be honest, since this is your first go around with having chickens, I'd wait and just raise up those babies and not take on the issue of having to integrate the babies with the older birds once they are ready to go in the coop. Chickens do NOT like newcomers, at all, and they can be brutal! Integrating new birds or young birds into a flock takes time and effort and for best results you really need a separate pen for the young birds alongside the older birds. That way everybody gets used to each other before they actually share the same space. Otherwise you run a big risk of serious injury to the younger or smaller birds. I keep young birds alongside older ones until they are fully 15 weeks old and the same size as the older ones. They still scuffle a little when they are allowed to mingle but it's very minor.