I am facing the same concerns. I have 3 Black Sex Link hens, I don't know how old, but they are older. 3 weeks ago, I purchased 6 Araucana pullets that were about a week old. All are doing great. They pullets have been kept in the house under a heat lamp since I got them.
My run is basically 12 X 20. The coop is about 6X6 and is in one corner of the run. I have fenced off the other 6X6 next to the coop. for the past week, I have been putting the pullets in the 6X6 pen and letting them run, fly and play slam dance with each other. My BSL hens have pecked one or two of the babies through the fence the first couple of days, no damage. Now they just watch each other.
Over the last couple of days, I have noticed new feathers on the pullets starting to emerge.
I put them out in the morning, check on them many times throughout the day, then bring them in around sundown.
First question: when can I let them start staying outside at night?
Second question: When can I start letting them actually mingle, supervised, with the BSL hens?
Third Question: When can I let the stay out permanently with the BSL hens?
I intended on only getting 4 Araucana's, but bought 2 extra in case if something happened, but it looks like I will have all 6 since they are all doing excellent.
I will look back at the sticky's and try to post pics.
I am a new chicken head, and am learning as I go.
TIA
Steve