I don't pretend that I am even close to understanding the complex family relationships that both Heisenburger and neopagan are facing. But these are people you love. People with whom you share a home. Perhaps one strategy might working on creating the kind of environment in which you can ultimately be honest with your family. What aspects of Christianity are important to them?
Heisen, it sounds like your mom is afraid that her life will lose meaning. I don't understand that. For me, my life has meaning because it is my life. Not a rehearsal for an afterlife. But maybe you can work on focusing on the aspects of your mom's life that have meaning outside of religion. Does she serve the community? Is she someone who others lean on, or does she impact on the well-being of others? Can you help her recognize the importance of her life outside of the context of religion? Can you share bits of science that make her feel awe? I love Neil Degrasse Tyson and Brian Cox and of course Carl Sagan. When I hear them speak, I, to quote Dr. Tyson, "feel large."
Neo, I LOVE your answer to your wife. It was so honest and clear.
I guess for both of you, try and pinpoint the aspects of religion that are important to your family members, and help them see that these things can exist outside of religion. Religion offers community, traditions, rites of passage, cultural identity, explanations for the world around us, a way to honor our ancestors and those who we love who have died, and it also provides a forum for moral codes, altruistic acts, and a philosophy of life. But each of these things can exist outside of the context of religion. All of them.
Good luck to both of you. Feel free to come here and share and vent. Share when you feel strong, and when you feel weak or scared or defeated. You have a challenging journey ahead of you.