YES keep them penned up at least a month before releasing them. Can you keep them in a corner of the coop during this time so they can acclimate to the flock? One where everyone sees and hears each other? I cannot tell you how important this is as I hatched 13 keets last year and kept them in a cage within a dog pen but I missed the latch coming out one night and they all were all over the yard the next morning. I was only able to catch one, which I still have, and the rest ran off into the woods
That was entirely my fault. If they hatch from a guinea you already have on the place I am sure you won't have that problem.

That was entirely my fault. If they hatch from a guinea you already have on the place I am sure you won't have that problem.