I'll add my experiences. I've had two different hens wean their chicks at 3 weeks. It was warm enough day and night that they did not need heat. They were raised with the flock so the hens spent three weeks teaching the others to leave their babies alone. I have a decent sized coop and plenty of room outside. I do believe room is important.I guess I just need reassurance that the chicks will turn out ok with less nurturing than I had hoped for.
At first the chicks were upset but they quickly learned they were on their own. They found their own food and water. During the day they avoided the other adults and the adults left them alone. At night they put themselves to bed in the coop. They slept on the coop floor at first but eventually learned to sleep on the roost without Mama showing them how. Probably at 4 to 5 months of age. They grew up to be normal chickens.
Good luck with yours.