If you have older birds they should teach them everything they need to know. I let mine out with the flock at around 12 weeks but they are in a mini run inside the fenced in area from day 1 if its warm enough.
When I did free range without a fence, my chicks were about the same age as yours and they did perfectly fine.
When I did free range without a fence, my chicks were about the same age as yours and they did perfectly fine.