It can depend on the personalities of the older flock and your management approach. If your flock free ranges, so the coop is only used for laying / sleeping then bullying should not be too much of a problem (providing one has multiple feed stations) but things may become a little tricky if your...
Hi and welcome to BYC. Not sure of your coop size / set up, but if you could put the young ones in a crate / separated area within the coop (once they no longer need heat) then it will make integration so much easier later on. Just gives a head start to the look no touch approach.