I am in the same boat. I have two we raised from chicks and we just bought two of roughly the same age from another farm.
So they should be separated for a bit in a "seen but not touched" type method? Is a week long enough for this?
I have a chicken tractor with a run, but I wouldn't consider it large. I was planning on using a cage next to the tractor, but that would mean the new ones wouldn't have anywhere to roost at night. Seeing where they came from, it breaks my heart to leave them like that. The new ones are super sweet. (Much nicer than ours, actually. I think I probably should've picked them up more or something.)