They're probably feathered enough to go outside, but they would do best with an escape pen. I create a small "panic room" in a corner of the pen. The youngsters are enclosed for about a week while everyone becomes acquainted through the safety of the fence. Then I cut small portals into the youngsters' pen so they can explore the bigger pen, but scoot back into their "panic room" if they get bullied.
It's also important to place their food and water inside this smaller enclosure so they can eat without being constantly chased away from the feeder. As they grow, you may need to enlarge the holes. They eventually reach the point where they're all pretty much the same size, and this enclosure will have served its purpose and you can remove it.
In the coop, I try to partition it off in the beginning so the youngsters aren't bullied at roosting time. But this seems to be of lesser importance, since everyone is usually single-minded at roosting time, and the babies will quickly learn to either get in and roost first, or wait until the others have roosted and then roost in the space that's left.
On that note, you can minimize trouble at roosting time by making sure all the different age groups roost together. Trouble seems to crop up mainly when someone gets "out of order" and roosts in between two of another age group. They're extremely clique-ish.