Don't have time to read the other posts, but I'd certainly bone up on all the major holidays, Christmas, even New Year's, Easter and Halloween, then even the smaller ones. Most all families due the Christmas, Easter and Halloween. The others, it varies from family to family. But those holidays bring such joyful memories to a child, that your child will grow up with different and much more joyful memories from those you had. Birthdays are kind of family to family, too. Some always have a huge party for the the whole family. Some just have a cake and give the child a present, that's what my family did, we'd have a cake with candles after supper, made a wish and blew out the candles. But even those memories, of seeing the cake sitting there in anticipation (oh, you need ice cream for the cake, too). Anyway, your child will develop wonderful, joyful memories that you probably can't imagine. My grandkids' belief in Santa is so joyful to see. They truly believe. And these traditions are not necessarily religious, there really was a man, a priest, who in some ancient times, used to leave boxes of clothes, shoes and toys on the doorstep of poor families from time to time in his area, and that's what started the Santa Claus tradition. I believe he usually did it in the winter, when he saw kids without warm enough clothes or shoes. So see, no religious attachment. So what if he was a priest, anyone could have done it and started the same tradition. And I read in ancient times, in Germany, people used to decorate the fir trees during the long dreary winters just to make things seem more cheery, so what's wrong with that? Nothing religious.
Anyway, that's my take on things.