Assuming you don't have/use a run, I would put up temporary fencing for at least a month...even if it's just chicken wire and a few green metal posts.
How long have they been in their coop? They definitely need time to learn that their coop is their safe zone/home before attempting free ranging. At seven weeks I'd be afraid of predators picking them off anyway, due to being so small.
Adding a small light to the coop will help lure them inside as darkness falls, even if it's one of those battery operated push-lights. Turn it on about 30 minutes before dark and off after everyone is inside. But that will only help if they already think of the coop as home.