How long are you away for? Holiday blocks are awful, don't use them, they can pollute the water really badly and you're quite likely to come home to a tank of sick or dead fish. Healthy, adult fish can easily go for two weeks without being fed.
Where are the fry now? If they're in a separate tank, they'll be fine as long as there's plenty of plants in with them as they will eat tiny bits of algae and microorganisms from them.