The whole point of this charade was to look like the perfect partner so as to give no room for anyone doubt your position as the wronged victim. Announcing you're gonna hook up with your cheating partner's ex the second after you've broken up looks really fucky when you're trying to court public opinion. We, as the readers, know there was nothing untowards going on, but that move will give the ol' "you cheated too!" card some legs to run with, muddying the whole issue. The better move would have been to cede the tickets to the second place couple and move on, separately.
The final chapter's already been posted, so I'm probably just shouting into the wind.