[X] You know you can't stop more from coming, but you can certainly delay their arrival. Cast a spell of protection over the town to keep out anyone who has harmful intentions towards the children.
[X] I'll set up wards, so many wards. Cover the place in spells to hide the kid's magic energy and protect the house. If possible I'll make something wearable for the kids, and make sure they always have at least a holy symbol. For younger vampires that should help, though ideally they'd also have a weapon at all times. I'm not sure if I can do anything to ward the town itself, but if I can I'll give it a whirl.