What about the girls' wishes? Maybe they haven't fallen for the other guy XD? I mean, till the very end they both happily said only good things about each other to their friend's fiance. Not once shown any sort of reluctance? Oh well, at least it was cute
It's not like it was a decision that was made after just one encounter. And the princes are smart blokes. And considerate to a fault. I highly doubt that they would pull off that kind of stunt without considering the girls' feelings.