Well after watching the movie "my big fat greek wedding", I could see some of the troubles that could happen if there is a wedding between two different cultures, for me one of the biggest problems is the acceptation of the families, because they may have their own reservations, they might not accept the customs of the mate, another problem could be the religion, if for one of the families of the couple the religion es really important it could be an obstacle for the wedding, if we remember the film Ian couldn't marry Toula until he turned to the greek ortodox church, and it would be worst if you try to marry a person from a more strict religion like the islam or the judaism, you couldn't even date that person, anyway if the couple love each other they will find a way to marry if they really want to, I think that the real problem are the families more that your couple.