I too, am interested in hearing what thinkers think in this sort of situation. My 2nd son, who at one time was a warrior for Christ, has since turned away and declared himself an agnostic/atheist. This hurts my heart so much, but I know I need to step back and allow him the time and space to come back to the truth he knows in his heart/soul. If I push too much, I could lose him for good, so I just continue to pray and love him to the moon and back.
My heart goes out to you. Our youngest son has also declared he is atheist, raised going to church and was part of the worship team when he was in high school. I take comfort in the prodigal son story and pray and love him. I know how much Jesus loves bOth your son and mine and will be continually wooing them back to HimSelf. Thank you for sharing your heart.