Not a whole lot you can do now., however, I'd make sure you seperate them as soon as it is possible to do so otherwise you'll be over-run with 'em before you know it.
Provided you decide not to take spacechimp's advice, I would suggest you do nothing other than make sure mum is well fed and left quietly alone to bring up her babies.
Make sure she has no access to a male as she can get pregnant again straight away.
Leave them alone for a few weeks so mother can feed and look after them but remember they reach sexual maturity at 4 weeks! You could end up with lots and lots of babies so separate them in less than 4 weeks!