I don't think it was coons, mine always attack in the night. Coyotes will get them in the day time.
But it really doesn't matter. The being featherless with wounds would be a much bigger problem with older birds, but not chicks.
I would set it up as you describe for a couple of days, then I...
Coons are my nemesis. Smartest predator, and heartless. You have my sympathy.
As for adding the chicks - I am in the camp, the sooner the better. I get mine in about 3-4 weeks. They need hide outs, and escapes where she can follow them.
Feed - feed everyone chick starter or all flock, serve...