Beforehand or at least when you arrive at the restaurant let the hostess know that you have some plans to play a game with your server and request someone who is fun-loving and will be a willing participant. When you are seated sit all the men on one side of the table and the women on the other in no specific order and giving no indication of how the couples are paired.
When your server comes over ask him or her to decide on the seating for the table, putting together who they think are the couples and explaining why. The party guests are not allowed to talk at all during this process or give any hints. Once your server is done keep that seating order for your dinner and take a picture showing the match made couples. Make sure to send a copy of the photo to all of your guests and you might also strongly consider giving your server a little extra tip.