Don't forget about the magical creatures that might exist in the same world. For example, a friendly witch who sometimes helps the little vampire out. Or a werewolf who is an unlikely ally during a time when both their species are in danger from a common enemy.
There could be a group of vampire hunters as characters. They are constantly on the lookout for the little vampire but never quite manage to catch him. And then there's the little vampire's family. His parents who are strict about vampire rules and his little sister who is always getting into trouble.
Well, of course, there's the little vampire himself. He could have a best friend who is a human, a brave kid who is not afraid of the vampire's nature. There might also be an old vampire mentor who teaches the little one about vampire traditions and how to control his thirst.