I believe the Guinea Lynx page links to this page, but I'll provide it just in case:
http://www.cavyspirit.com/sexing.htm. I found it extremely helpful when I had to sex a baby guinea pig myself. You will want to recheck in a week or two to confirm, and by three weeks you must be positive because the males need to be separated at that time to avoid more pregnancies. If you are unsure, you can post pictures on this site and we will help you. I also recommend seeing a competent exotics vet to check for you if you still aren't sure.
Make sure to feed mommy and babies lots of extra veggies so they get all the vitamins they need. Alfalfa hay can be fed as well to provide additional calcium. Check the "Diet and Nutrition" forum to do some reading on what it's best to feed.
I know this must be very overwhelming for you, but don't worry. Guinea pig babies are born as little miniature adults and they need very little special care. You have already gotten through the hardest part, and now you can relax and enjoy your new little piggy family. We are here to help if you have any more questions or concerns.