Ok now this sounds like a lot of fun. I would love to do a maids cafe and I do think it would bring in both people and money. I would so love an excuse to get a maids costume made.
As for the tea party I have seen people buy their con passes just to go to one before but that was at a anime con and I don't know if Mobicon would be the same.
But all in all it's a really good idea.