A worm should be just fine... mine were eating whole grasshoppers. Just make sure they have eaten some grit or rocks before-hand to make digestion easier for the 'lil cuties
We give our chicks worms often, they love them. We just give them worms that are appropriate for their size. No night crawlers for the newborns! Also because the worms are soft they can eat them even if they have not had any grit yet.
They love moths also. So much fun to watch them chase the moths around.