Most of us are eager to get them into the coop, but if you already have a full grown established flock in there, it might not be such a good idea. Full grown chickens could injure or kill the younger, smaller chickens. They could keep them from the feed or water or chase them out of the coop and not let them back in. Anything could happen really.
It's kinda like letting the grade school kids out to play with the high school class. You'd like for it to work and it usually does, but sometimes it goes bad real fast. So what are your options?
You could put them in the coop but separate them from the adults for awhile. Large dog crates work pretty well for this. Or you could put the chickens in a grow out pen instead. A grow out pen is pretty much what the name implies: a fenced in coop and home for the chicks to grow up a bit before they move in with the adults.
