Christ?mas

I'm decorating the apartment for Christmas. We don't have a lot of space so its a just little things. A small fake tree, some lights and a few knick-knacks. As I'm putting them up I can't help but think about what Christmas means to me and what to teach the boys about it.
Santa is a must. I firmly believe that belief in Santa, and other childhood fantasies, is beneficial to children. Terry Pratchett (a favorite author of mine) said that we need to believe in small things there is no proof for as kids so that when we grow up we can believe in the big things like Justice and Hope. These things are creations of the human mind and for them to be real we have to believe in them.
But I'm at a loss on the religious aspect of the holiday. Matt is an agnostic and I'm a lapsed Catholic, reluctant agnostic and generally indecisive on the matter. For all that I am very involved in the boys' lives, I am not one of their parents so its not really my call as to whether or not they are introduced to christianity or any religion and when. However, if Matt and I have a child together then I will have a say. I just don't know what that say will be. The boys are still very young and another child a few years off at least so I guess I can put off the decision for a few more years and just enjoy this holiday as is.