From what I know about breeding gerbils (basically similar I would imagine in how they care for their young) as well as from some of the posts that I have read on here, you don't really have to worry too much about the babies right now. Just make sure that momma has plenty of food and water, I would keep them on regular bedding (wood pellets, aspen, whatever you usually use, I used to notice with my gerbils that they will push it all towards where the nest is, I believe that rats may do the same also, plus you wouldn't have to change it as often as paper towels and newspaper), and give momma some nesting material (some old cloth, torn up newspaper, I used to use old phone books... just tear strips out of the pages). But mostly at this point just take care of the momma like you would normally do and she will do the rest. I would just be slightly more cautious at first around the momma, some of my gerbil moms used to be okay with me being in their cage, others would try to run and nip at my hand (they were just being protective mommas, normally very nice girls). Good luck with the new babies!