I would put them in soon, adding more birds to a single is very different then adding a single bird to 5.
But I would set up an area in the run, that the chicks can escape too, the sooner you do this, the bigger the difference in size, which makes the one way gate more effective. I have used lattice panels, 3 week chicks could run through like water. I have also put fencing up 5-6 inches off the ground.
You put the chicks in the safe zone, and wait, eventually they will come out. You give a mock chase, so they scurry back to safety. And that is it. This way they all work out the relationship on their terms. If the old biddy gets too crabby, they escape. With that many, she can't chase all of them. Chasing is tiring work. A week and you can probably take down the barrier.
Do make sure that there are multiple ways to get into the safe zone.
Mrs K