They are old enough, and the first few times out, they probably won't go very far. But make sure the first few times you are prepared to stay up until after dark!
Young ones seem to like to push it to the limit when it comes time to go in.
I can almost tell you the ages of my chickens just by the time they go into the coop. The older they are, the sooner they go in. My 4 year olds go in about 2 hours before dusk, the 6 month olds don't go in until it's almost time to bring out the flashlight to make sure they all go in.
When I start letting new young ones go out, I wait to feed them until very late afternoon, or early evening.