Not sure and maybe it will be fine, but you may have put yourself in a wreck trying to do the right thing. At chicks 8 weeks old, all the broody instinct is gone from the mother bird. When you add her back to the flock, she too will have to fight her way in, she will not protect the babies. One needs to add them to the flock when those hormones are high. However, that is hindsight.
The big question might be, how many birds at each age, and how big is big space? Makes a huge difference.
I am questioning your space and set up. If I take it right, it sounds like you have 3 set ups, the separation area, the coop/run, and a large yard. I would put the big girls, including the mamma birds, out of the coop to free range in your back yard, and lock the littles in the coop/run so that they can explore the set up without being attacked for several hours. I would then let them back in their current set up, let the bigs back in, all go to bed in their current positions. I would try this for a couple of days. Then I would let the bigs out, and later, I would let the littles out in that big yard space, again with hideouts. I would let everyone sleep where they want. After a couple of days of this, I would close up the separation coop.
Make sure you have plenty of hideouts, and extra waters and feeders. I don’t think anyone will fly out, but if you posted pictures, it would help. Large space means different things to different people.
Letting birds explore an area, without being chased, or being chased by you to find the hide outs, can help.