I want to say preferably don't go as an Ouran character that's already being cosplayed, so we have our one group running things like a real host club ball and don't have to deal with duplicates. But if you want to be some other character in the school, there may be a need for leads, or in general "guys" that can ask girls to dance. What is the gender ratio normally like at this type of event?
There isn't space to spare for a dance instruction panel, but everyone should definitely start preparing now, so as to lead people in dancing at the event. There are a lot of dance instruction videos that you can find online, and I'm sure you can find a friend to practice with. We can meet up beforehand somewhere at the con if anyone wants last-minute practice then. As for those friends that can't memorize the steps but will ask people to dance, that's fine - their help is needed just as much, to break people out of their shells and get people to have fun!