No no no. You're doing it all wrong. You work up the courage to invite the girl you really like, then later a misunderstanding will happen and the other girl will think you invited her. And instead of coming clean you try to take both girls without the other knowing. You'll try all night to bounce between your two dates without raising suspicion. But you'll cause a series of hilarious mishaps culminating in both girls bumping into one another, blowing the whole thing up in your face. Jeeze hasn't anybody scene a 70's sitcom, for pete sake?
I kind-of want to see this now, but the other two girls also accidentally agreed to go to the prom with each other, due to an unrelated misunderstanding, and they've arrived at the same conclusion for how they should handle it.