Well here's what I think:
It would happen on a Saturday night at Hogsmeade, at the Three Broomsticks or something. So whilst the students are out at Hogsmeade during the day they'll see posters and adverts for the night and the single folk think 'hey that sounds cool, maybe I'll go along'. But it's late at night and they're not allowed out at that time, so they all sneak out but without knowing that other people are sneaking out. Still with me?
And they all do the speed dating thing. [Speed dating is basically where, for example, girls are seated at tables and boys will sit opposite a girl and talk for, say, five minutes before moving onto the next one etc.] Then when they sneak back into Hogwarts, Filch is out on the prowl so one by one they randomly bump into each other around the castle. e.g. Edward bumps into Sergei and then later on bumps into Heather and so on. And in the end Filch catches them all and then we can rp a big phat detention in the Forbidden Forest. XD
What do y'all think?