How formal is the wedding? If jacket-and-tie formal, go to a tuxedo rental shop and rent a Spencer jacket and wear it with a white shirt and regular tie. If less formal, just rent a 5-button waistcoat and wear it with a tie. If the wedding is casual, then wear a white shirt and tie, and if it's hot, skip the tie.

You are going to be juggling twins-- nobody will worry (or notice) your jacket.