Today was the big day when the barrier came down and the broody and her chicks were free to go meet the flock. It didn't go the way I imagined it... After all that rushing to go out, it took her several HOURS to decide to actually try to go out. And when she did, the chicks didn't want to follow. She'd go out and call them, go back in, go out again and call them, and so on. Clearly really wanted to take them out. But they were like NOPE not happening mama!

Finally, only one of the chicks finally made it outside, by complete accident, but its grand exit was quite epic:
I spent about half the day out with the chickens, to observe the interactions once the barrier came down, and to make sure all was well. Some chickens went into the coop to investigate the babies, and some investigated the one chick that went outside. Whenever one came too close to the babies, mama left the interaction with a tuft of feathers in her mouth:
That made me feel better about her ability to protect the babies. I was starting to doubt her because she's so incredibly nice to me, and even to the kids (!) whenever we're around. She lets us come close and pet her and the babies, even all three of us crowding the coop and hovering. By comparison, my friend who lent me the incubator and whose chicks I hatched along with mine (and whose chicks the broody is raising), also has a broody right now, and nobody is able to come anywhere near her because she goes into a rage and flies up and attacks everyone, including my friend who's her primary keeper. So I was worried that my broody wouldn't be able to protect her chicks out there, but now I realize that all the time and effort we've put into handling and socializing her and bonding with her is paying off. She trusts us, and that melts my heart
I felt bad for the other hens though. None of them seemed to go after the chicks at all, or even seemed interested in them, but the broody kept making the "I found food" sound at the chicks and pecking the ground, and the other hens were responding to it and coming close to look for food, only to get smacked as a result.
So I think the first day of real integration went fine. Only one chick spent time outside (while the broody paced frantically back and forth between it and the others inside), and not all the hens interacted with the broody and the chicks (that I saw), but there were no accidents and no ill intent on the hens' part, and the broody is definitely protective, so I feel better about it.