You know, if he wanted to fight against vampires Naruto and friends could all just go as Van Hellsing, or something. Or a adventure team... Or maybe, if they really want to win, they could go as Garlic, Onions, Silver, a Wooden stake and a UV Light.
Or the Dragon Born. He deals with vampires and the undead all the time! But Kyubey is good too, I wouldn't want to go near that bastard for all the wished in the world!
Leave it to Naruto to dress up as something fox-related. I'm guessing Shikamaru decided not to dress up this year. Ooh! I don't know if you already have the entire plot planned out, but maybe you can sneak the ghost of Minato in there and make Naruto freak out! That would be funny! Only if you want, though.