I love giving out Christmas cards, and when I address them to my friends and family, obviously I address them to the person and their significant other. My question is, when I address Christmas cards for co-workers, that will be given out at work, should I address it to them and their SO, or just to my co-worker? In all but one case, I haven't met the SO, as my relationship with most of these folks is strictly a working relationship. Thoughts?