While I have never truly been a Christian, I have only recently decided to give up the charade since turning 18 (a couple years ago). Though not around family. My extended family are fairly devout moderate protestants who are closely knit. The entire family is well educated, everyone is expected a bachelor's degree at the bare minimum, and everyone of age has at least a masters. Though we live far apart, my mother's side always comes together for Thanksgiving, Christmas, and summer break for 1-2 weeks each. During these times, I've lapsed back into the charade. I always feel guilty to myself, so lately I've firmly decided to never partake of the charade again. I will not be attending Thanksgiving this year so I have sometime. However, Christmas is looking ever more intimidating. On principle, I do not question the religious beliefs of others and so do not impose mine on others. However, I know that even in silent dissension I will be "found out" at the very least when it comes to Christmas Eve service.
That being my rough background here is where I seek advice. How should I approach this conflict? My nature has me do nothing until asked why I will not go to the service and must respond with revealing that I am an atheist. I know this is going to be a terrible event for everyone, especially considering the holiday. I know I need to communicate this to my parents first, but I am at a loss as to how to do so. I suspect my father knows of my non-belief, but I am sure it will destroy my mother. It is out of sympathy and respect for her that I have yet to reveal my beliefs. How do I break it to them?