You know, a simple litmus test might be to ask yourself the following. If I send cards saying Merry Christmas am I sending a message inclusive for those who don't celebrate Christmas? No If I send cards saying Happy Holidays am I sending a message inclusive for those wo do celebrate Christmas? Yes The former excludes every non-christian and even some christians. The latter includes everyone during the holiday season regardless of traditional origins or cultural differences. If your goal is to truly reach out and send a message of happiness and cheer, why not choose the option that is most inclusive and if you want to promote a spirit of togetherness, why not choose the option that recognizes differences in cultural interpretation of the holiday season and illustrates a respect for those differences? Choosing the option to send the cards that specifically highlight your personal beliefs would seem to me to be sent less in a spirit of comraderie and more an assertive statement, or a spirit of defiance. After all, "Happy Holidays" or "Season's Greetings" includes those who do celebrate Christmas. So the only sacrifice you are making in choosing a more general greeting is that you are not allowing the imposition of your specific belief to overshadow an underlying genuine expression of love, togetherness, and hope.