You don't have to tell your family until you are ready. If you are young, then you shouldn't practice witchcraft if you think your family wouldn't like it. That doesn't prevent you incorporating some small witchy practices into your daily routine.
Shape shifter spells won't work because there is no such thing. Witches are human beings who practice the craft of being a witch. They learn how to make change happen by manipulating energy. However, they can only be changes that work in conjunction with the natural world. Shape-shifting is nothing but a construct of myth, fiction writers, and Hollywood.
There are plenty of Christian witches out there. There are also many who think that the Bible states that 'You shall not suffer a witch to live'. It's a mistranslation. The original text referred to poisoners. Some people say that Jesus was the greatest witch that ever lived.