This is a personal decision. Lots of folks on here also free range, including people who have had chickens for many years. But it is a risk, and sooner or later will no doubt cause a loss or losses, perhaps to a stray dog, perhaps coyotes or a hungry fox. I have done both. I've gone for months free ranging without a loss, when I had two dogs who were quite good with the chickens and who chased predators away. Now I have 11 birds in a large fenced yard, about 70' x 70' -- not predator proof, of course, but no losses for over a year, I assume because there is enough food for the local predator population that's more easily accessible. I can live with fencing them in a yard large enough for bushes and grasses to grow (mostly because of coyotes and stray dogs in my case) but I personally would not keep them in a "small pen," which to me the usual 10 sq ft per bird is. Having a guardian, such as a donkey or a well trained dog or two, does improve their chances greatly.
It sounds like in your case this is something you need to discuss with your kids. Of course we assume (and I believe) the chickens prefer being free range; it's their natural condition. Freedom vs. safety is clearly a complex subject with many variables, some of which you mentioned.
