I was under the impression the bigger girls would hurt or be mean to the babies. I also don't have an ideal place to keep the babies so I though about keeping them shut in the coop until they could come out during the day.
Will PM you now, thank you!!
Is there a way you could make a little partition within the coop for the babies? My coop is tiny (6x9) but the back is a shelf (3x6), and I can partition off either under the shelf or the shelf itself for two seperate isolation areas, which is nice for new chicks. It doesn't take long for the littler ones to be big enough to hold their own- maybe 8 weeks max, especially if they see each other in the mean time.