Your kids sounds wonderful!
You should seperate them ASAP or else you will have a lot more (as mentioned above) Gestation period is about 24 days, and pregnant again after 12-24 hours?? Average litter size of about 12.... That's A LOT OF BABIES!! And first litters tend to be less then later litters... So you have 6 right now... you can expect more the next go around...
Spaying and neutering BOTH have their advantages. As mentioned above, Spaying reduces the likelihood of mammory tumors in females and can add some time to their life span. On the other hand, it is normally more expensive considering the surgery is more invasive. Neutering often reduces aggression in males and is a lot cheaper! My vet neuters for $35. But I wouldn't EXPECT a price that low. I have gotton quotes between $30-$250. Just call around! It never hurts to ask!!
What kind of bedding are you using for them? And what kind of bedding are you using for the new borns??? Make sure it doesn't contain any perfumes or too much dust (preferably none). Aspen is great but DO NOT use Pine or cedar! I use liners in my cage and it works really well! I would suggest it to anyone! I can get you some names of people who make liners and other accessories if you just PM me!
What food do you use?? There is a lot to know about food for your little ones and you can learn it all with a little research! I suggest Harlan Teklad Lab Blocks, as anyone who has experience with rats would!
I Hope I answered some of your basic questions! Goodluck with those babies and get those boys and girls SEPERATED!! The babies also need to be seperated at 5 weeks or they too will be pregnant! Momma does not need to become a g-momma!