Just the three of us is fine by me, as for the fourth contestant I'd say that depends on which House we all want to claim. I personally would prefer to have Ravenclaw or Hufflepuff myself, so I'm putting my vote in for those.

If the open slot ends up [I]not[/i] being Gryffindor, make it AU and we can make an NPC for it. It it is Gryffindor, make it Harry *shrugs*