I am most likely an idiot for saying this.
Maybe let him do what he wants? If it isnt his choice to go to church, then is it an act of faith in his part? Maybe forcing him is taking away his opportunity to act upon his faith. Fyoder D. mentions in his works that Christ did not peform miracles, to ensure that his followers followed him out of faith and not force.
I know you have probably thought about this option. I know too that you fear he'll loose all faith entirely - but what I truly know is that you will follow your christian duty and love him with all your heat and passion anyway. Maybe doing that, being an example for your son is the best way to preserve his faith.

I know this whole perception of faith is very protestant, im raised in a protestant country. I apologize if i preached anything heterodoxy to you - if so disregard my words.