You might try this. It might work.
- take your chicks outside in the cool of the evening. They need get chilled. And pretty chilled, peeping madly. It won't kill them, but they will want to be under the hen in that nice warm spot
- wait for solid dark, your whole coop needs to be comatose. Take the peeping chicks down there, wait a few minutes
- wearing a thick sweatshirt, stick the chicks underneath her, one at a time.
- If one crawls out, stick him under there again.
- Cross your fingers and wait outside the coop
The hen should begin to cluck differently, almost a steady beat. The chicks should get silent and go to sleep.
They are a little old to try this, if they were 3-5 days, I would be sure it would work. But if you get the chicks cold enough, that a warm spot feels good, it is your best bet. It won't kill the chicks.
Mrs K