aww how cute! I wish my dalmatian mollies would have some fry. I think you can crush up flake food really really small and feed that. As for what to buy for the babies maybe someone else can help-or maybe do a search.
Now you've got the fry leave them in the net breeder or their own aquarium, feed them little and often - 3 times a day for maximum growth- with finely crushed flake food (as fine as you can crush it, use your fingers and rub them together really grinding it up very finely because any large bits will remain uneaten and will rot polluting your tank). When your baby fish have grown to about one inch which will take between two and four months you can release them back into the aquarium with their parents or this is also the size when fish stores will be willing to buy livebearer fry off you.
Finely crushed up flake food works just fine, or if you're worried, you can buy Hikari First Bites, which is flake food crushed into a very fine powder. Liquifry is also another option (food suspended in a liquid) but I'm not too fond of it because it fouls the water too easily, IMO.