Atheists/agnostics/nones

Let me preface with I'm a non-believer so I'm not asking to attack you. Also, posting anon so I will feel less inclined to argue with the people that say I shouldn't enjoy the holiday bc I am not Christian. 
Question: Do you celebrate Christmas and if so how do you/would you explain the celebration to your children?
I ask bc I still "celebrate" the holiday it is one of my favorites and  I love the time with family but I'm wondering how to go about explaining it to kids.