You should be ok. My backyard fence is only about 4 feet high and we haven't had a problem with our girls getting out of the yard since they've gotten large enough that they don't fit through the chain link or the small spaces where the fence meets buildings. If you are concerned about them flying over the fence, just clip their wings before you let them out. If they are used to their coop and run, they shouldn't go very far, especially when you first start letting them out. Now that it gets dark before we get home, I let my girls out to "free range" in the yard when I come home for lunch, then put them back in the run before I go back to work. The first day I herded them in by walking slowly around them and "funneling" them into the run (their run is about 2 feet away from the fence, so I put up a metal dog crate panel to block that access when they walked around that side). But since then, I find it much easier to get them into the run voluntarily by bringing them a bowl full of goodies when I go out to shut them up. If you choose a distinctive looking bowl you could easily train them to go to their run for treats from that bowl by using said bowl to bring them treats and feeding them in the run every day for a week or so. I don't really have a distinctive treat bowl, but I do have a treat call (I use a soft "chook, chook, chook" every time I bring them goodies) My girls don't beat me to the run yet, but they do follow me right in when I bring out their treats and aren't bothered when I shut the door to their run.