Will the hen go back to the coop when she is ready? Probably. Will the chicks? Who knows?
My situation is a bit different from yours since my hens hatch in the coop and my area is inside electric netting so they are a lot closer. But sometimes I move the hen and chicks to a shelter inside an electric netting after hatch when the coop is really crowded. After locking the hen and chicks in that shelter two or three nights the hen always takes them back to that shelter to sleep. I’ve done that several times, twice this year. I’ve gotten different results over the years.
I’ve never seen any of the hens take the chicks to the main coop during the day. They always stay outside foraging. I do feed and water in several different places and they mingle with the rest of the flock as soon as I open that shelter, usually after two to three days.
My hens always go back to the coop. Most of the time this is after she weans the chicks. She leaves them in the shelter to fend for themselves and goes back to the coop alone. I have had a few take the chicks back to the coop before she weaned them, usually taking them to the roosts, but this is kind of rare. There is no roost in my shelter. If the hen does that, the chicks sleep in the main coop after she weans them.
I’ve had hens wean them at three weeks, I’ve had some go at least nine weeks, and leave them in that shelter. I’ve had very few broods of chicks move into the coop on their own if the hen abandons them out there. A few have but normally I move them myself. After dark and they are in that shelter I catch them with a fishing net and lock them in the coop for the night. They have been mingling with the main flock for a few weeks without the broody hen to protect them, but I’m still down there pretty early the next few mornings to make sure there are no serious issues when they all wake up. So far it hasn’t been a problem but with living animals you never know.
When I move them I lock that shelter so they cannot go back inside. Most of the time they go into the main coop on their own after that, but occasionally some or all try to sleep next to or on top of that shelter so I have to “herd” them or catch them after dark and carry them to the main coop for a night or two. The way mine is set up that is not all that challenging. It sounds like your set-up will be more challenging. It would not surprise me if they sleep in the tree when you lock your shelter. If I were in your situation I’d be strongly tempted to build a shelter in the main coop and confine those chicks in it a few days and nights to get them sleeping in the coop instead of the shelter.
Maybe an easier way to achieve his would be to move the broody and her chicks to the main coop after dark before she weans them. Just lock them in overnight and let them go the next morning. See where she takes them to sleep that night. I’d leave that shelter open in case she wanted to take them back out there. I’d be concerned she might teach them to sleep in the tree if she’s not ready for them to go to the coop. They’d be harder to catch in that tree.
