I'm writing this as someone who doesn't celebrate Christmas in either a religious or cultural sense. From a young age I was told that Santa doesn't exist and is just a silly hoax that parents play on their kids. It never affected me in any bad way and neither was I expecting to find wrapped presents mysteriously appear on the morning of the 25th day of December. If anybody in my family received a Christmas gift then it was usually opened on the same day. A downside to this is that even from the age of 4 or 5 I went round telling kids at school "Father Christmas isn't real, it's all made up, your parents buy Christmas presents from the shops" which often resulted in me getting into trouble whenever they got upset. I once had to report to the head teacher after completely reducing a classmate to tears.
Is the concept of Santa a silly nonsense or is it part of the joys of childhood? Do you tell your own children the truth or would you prefer to go along with the cultural norm? Is pleasing one's classmates more important than knowing the truth? What about children at school who follow different religions so do not celebrate Christmas - where do they fit in?
No matter how much you tell a blind man about the colour blue they will never understand it.