Sounds like you are quite observant. That is quite a helpful quality for a chicken tender, especially one of a free range group (or more).
Awareness does come with maturity, but acquiring the necessary skills and learning necessary behaviours for free ranging is easier to do at a young age.
Youngsters here go out ASAP. Brooder-raised chicks are at a disadvantage, since they have to get integrated first. Like yours, 10-12 weeks is when they usually get to out. A big difference is that the group of which they are a part of is multi-generational. Hens and roosters with years of ranging experience. That is surely helpful for the youngsters, gaining foraging skills and predator awareness.
For your bunch, I’d think supervised ranging for a few weeks would be the safest option. At the 16 week mark, they should be more than capable of doing everything by themselves. Should be safe (as much as one can be, when free ranging) to leave them alone even before that, if they have assumed their roles in the group. Someone to watch out for predators is most important. That usually is the male’s job, but one of the girls can definitely substitute.
There are no guarantees with live animals. Much less when free ranging. Setting them up for success is all that we can do. Plenty of cover helps. So does knowing the predators of your area, as well as your chickens. Seeing as we’ve introduced the chickens back into nature, working alongside it, as opposed to against it, is the safest bet
