Question about after prom?

Im goin to after prom and me and this girl r gonna be dancein a long time. wer gonna be grindin these no doubt and im probably not gonna be able to keep it down for that long will shes grindin. so should i wear like biker shorts under or not? plus were probably gonna be doin some dirty stuff after and i dont want her to see that i was wear biker shorts.. wut to do?