I wish I could offer some practical advice, but my family is slowly but surely coming out of it by themselves. So I haven’t needed to do any magick for it. So just to help with the brainstorming process I’ll add some ideas. It was said earlier to identify what needs they are having fulfilled and try fulfilling them in another way. I think that’s a great idea and I’ll propose some needs you could meet
1.) Community- when people leave the church one of the main complaints is loss of community. If you could magick to give your family members friends outside the church, and then give them a non religious community to be a part of, then the church will have less of hold on them.
2.) Purpose- learn about your families passions and dreams. Then do magick help them come to pass (in a way that does not involve the church). You don’t even have theirs dreams come totally true, just set them on the path and remove any early blockage that could cause them frustration. When they are doing what they love it will become more important than the church.
3.) Absolution of guilt- Christianity sells people the idea that they are broken, guilty, and unworthy then sells them Jesus as a antidote. They create artificial demand because they control the supply. Spells for self esteem and confidence can destroy that demand. Derdekea is supposed to help with guilt.
After that I think causing some turmoil in the church would be good. In fighting, cliques, general mean spiritedness. The point is to drive a wedge between your family and their church(s). And anyone that has been in church knows that these places are a breeding ground for these base emotions. Maybe do a working to make sure your family doesn’t fall into the chaos.
I also think getting rid of the pastor is good idea. A lot of people I know that left left when they had a new pastor and the church was in transition.
Then I would start on workings to cause them to doubt and be disgusted by Christianity. Banish people that may pull them back. Then a working for them to find their true spiritual path.