Hmm, this is an interesting question because I'm in pretty much the same position with my family. If they knew of my Atheism I think I'd be smited on the spot. However, I don't believe in morals in the sense that most people do. In my mind, it's more of a survival/this-makes-me-happy-so-it-must-be-good kinda thing; my idea of morals sort of goes back to the primitive, savage human (or so I've been told) before government and religion was invented (please pardon me if I insult anyone by saying this; this is not my intention). Hopefully I've explained that enough. So in my mind, I'm not being amoral or immoral or anything when I lie about my beliefs; I'm surviving so I'm fine with lying for the time being.