How do I break it to my mother that I follow the Wiccan religion? ?

My mother and grandmother are strong catholics. I don't follow the same faith, I never really did. My mother thinks that followers of the Wiccan religion are satanic. My grandmother believes that anything that isn't in the bible is fake and evil. How should I go about breaking the news to them, that I don't follow their religion, without getting kicked out of the house? (( I'm 17 by the way))