I think you post your blog too early. I like the total back and forth and for the two to three that may read it, I think they miss some of the fun. Jews are what they are but at the end of the day they are Jews. As a rabbi, you should try and get them to come and participate but do not get too frustrated if they do not. Without having any empirical evidence, I would be willing to bet that of the assimilated families of different religions, that the Jew tells the spouse that the religion of the children should be Jewish.
By the way here as some more Christmas songs written by Jews.
I suppose the reason Jews writing seasonal implicitly Christmas songs is that we are a small people. Because we don't possess strength in numbers, we truly need all hands on deck. Any energies that are diverted to ends that don't serve our purpose, the realization of the Torah in the world, are a waste. This is the problem with assimilation in general. Jews give to the general culture but they don't give to their own culture. As a result, our own culture stagnates. When a group has limited resources - in our case numerically - then we can't afford to have Jews devoting energy to frivolous purposes, especially those that undermine our relationship to the calendar and the seasons.