I would say if you have them in a tank in a busy room give them a plastic hide. If they are kept away from noises they may be okay without one. Mine pile up extra bedding around where they give birth. They all share babies too, even my mice that haven't given birth will nurse the babies.
@ hedwigdan These babies are 3 days apart. Both moms nurse them as well as one of the females that hasn't given birth yet. The bigger ones are 4 days on and the younger are a full day old.