Welcome to BYC. You can kind of train them. When ever they wander too far, use a bit of scratch in a container to call them back. Shake the container while you call them. They will come running for a few grains of scratch. The big issue I see is your yard is very open. They will be prime targets for predation from both land and air. They will have no where to hide. An other concern is that, unfortunately, manufacturers of pre-fab coops misrepresent their product. "They say this coop will hold 8 birds." While the most common recommendation is for 4 s.f./bird in the coop and 10 s.f./bird in the run. (the coop is the closed in portion where they sleep at night. You could increase your coop space by closing in the upper level all the way across. Many of these pre-fab coops also lack adequate ventilation, and the perch size is on the small side for good foot support. Less than space that most often leads to behavior problems, aggression, birds being more prone to disease due to stress from being crowded.