They aren't going to mother them unless they are already broody and have been actively sitting on eggs. Then you could tuck them under one of the hens at night and remove unhatched eggs. But to just take some chicks and put them in with your hens is bound to result in heartache for you, dead or injured chicks, and stressed out hens. Now, I know that some hens are just natural mothers and will indeed take care of chicks that way, even if they aren't currently broody, but not very many. It's just not worth the risk.
I'd recommend putting the chicks in some kind of enclosure within the coop so that they see each other and get familiar, but can't come into physical contact. You can then begin integration - gradually and under supervision - in a few weeks. Good luck!
