guppies are prolific breeders (check out the livebearers section and my 'I think my female guppy is sick' for an insight) Generally they will give birth every 4-6 weeks but I've known my female to drop a few then drop a few more a few days later. They can also hold sperm for up to 6 months - just to make things more complicated.
Mum and Dad and any other tank mates will eat the fry either at the point of birth or several days/weeks. If they are small enough to fit in their mouths they will eat them. It's nature at it's cruelist. The male will be chasing to either mate or to eat the fry as they are born.
If it was me I would leave them to it. If you try and save every single fry that is born you could end up with 500+ fry in 4 weeks!
All I do is take out any that I find during maintenace and put them in a small tank. I take them to my lfs for them to sell on when I have a few.
