A DA letter can not be undone. It is unlikely you will ever have a relationship with your family again, and you will be considered a hateful apostate.
If you fade, they still won't talk to you much, and there will be things you can never tell them, but at least you can see them sometimes.
and like freeemind said, you can be a secret Wiccan! Wiccans were always good at being secret anyway ;).