What I did was to create another field by clicking the green plus sign next to spouse added area and I selected a field I knew I would never use like "manager" and in this field I created a line for how I wanted the envelope addressed like "Mr. & Mrs. John Smith", or "John & Jane Smith", or "The Smith Family".
Then I added a new "Group" to my Address Book called "Holiday Cards 12", and I dragged every person I wanted to send a card to to this group.
Okay, now here's the bad news. I wasn't happy with the results I was getting trying to print from Address Book so I purchased "Labels and Addresses" by BeLight Software from the App Store. You need OS 10.6.8 to get on the App Store. They have a version available for purchase for OS 10.5 on their own website. It has excellent Video Tutorials to walk you through the process, and it imports your information from the Address Book. Here is the link:
http://www.belightsoft.com/products/labelsaddresses/overview.php
When I finished printing my mailing labels, I even created some very nice return address labels on it.
Sorry I'm not better help.
Good luck.