If it were me, I think I'd put the two youngest in the same room, and then have your older two dck's could bunk together in another room. I'd be reluctant to put siblings in the same room just because sometimes kids will pull stuff with their brother or sister that they would not try on with another child. (i.e. not settling down, making a lot of noice during nap time) Maybe you could try "training" your current dck's to sleep in a shared room a month or so before the new babies arrive ? Hopefully, by the time the other two children start up they'll know the drill for naptime - lie quietly, no chatting with the other children in the room, etc. It also allows you some flexibility if you have to use the CIO approach with your new babies. Good luck !