Hi,
Since guppies are livebearers, the fry are born quite large, compared to a goldfish fry. They are easy to feed with a prepared tropical fish food for fry, or even finely crumbled flake food.
As the previous poster mentioned, get some fine leafed plants for the babies to hide in, preferably water wisteria, as it floats and the babies like to hide up under the leaves and in the root mass.
Also, if you want, you can get one of those little breeding traps, and net out some of the fry and put them in there, just for a week or so, until they get a bit bigger. Sometimes, unless you have lots of hiding spots, the adults will eat a lot of the fry.
Also, I would suggest keeping just one colour or strain in the tank, since they do interbreed and you would get less desireable colours with a mixture of colours and strains. Also, get more females to males. The males chase the females constantly, so it is a good idea to get about three or four females to every one male
Good luck!