I'm not an expert on Jewish law, but I would imagine that sending a devout Jew a Christmas card is tantamount to sending a power drill to an Amish person. It might make the sender feel good, but it shows that he cares little or is ignorant of their beliefs.
Sorry, I have several conservative orthodox Jewish friends who keep closely to the Torah and they have accepted Christmas cards and gifts graciously. Accepting a gift is not like participating in a ceremony (and yet I did participate in many of their ceremonies as a gentile observer). Being respectful of other’s beliefs doesn’t mean you have compromised yours.
Every year we invite several of our friends to our Christmas Eve open house. We understand that many of our closest friends will spend that evening with their relatives, so we’re never hurt when they don’t show. However, we have had the same three Jewish families come every year for about ten years now. They always express their thanks for our remembering them, because no one else invites them anywhere for the “real” Christmas parties.
Aaaaahh — there's the problem! Imagining that Baba Wawa is a devout Jew! You're displaying your lack of knowledge about Judaism — and about Baba Wawa!