even with adding new adults with the smaller chicks I have out there, chicks are maybe 9-10 weeks old maybe older and 3 that are a couple weeks younger.
Yes. Just keep an eye on them. If the older ones harass the babies, separate them until the little ones get a bit bigger. We don't separate our's even when a hen hatches biddies. They are all out in the yard together.
ETA: I am not saying that it doesn't happen or won't happen, that they won't fight each other, just say'n that we have never had any issues.