I have only recently begun keeping chickens. I have 15 adult hens, and 9 4 week old chicks. I read somewhere on BYC to put the younger ones in the coop or run, but to seperate them while inside. I do this by putting a large dog kennel inside the run and the chicks go in there with their own food and water. I put them in once its warm enough outside and then take them out when it cools in the evening. So the chicks are spending their days outside with the other hens but in the safety of their own "run". The dog kennel I use is one of the wire ones, no plastic floor or walls. This way the babies can scratch and peck the dirt, and dust bathe. The article I read said that doing this for a while will introduce the chicks to the hens while being safe to the chicks. The chicks are enjoying it, and the hens don't seem to mind either. The chicks go back to the brooder at night, which for us is a large water trough with straw and a heat lamp.
So this could be a way for you to minimize the hen pecking, by using a slower introduction to the others