I had a conversation with my son (when he was around 30) after I had faded out. I wanted to see if he harbored any ill will towards me for 'depriving' him of a normal childhood. I was a convert, he was brought up a Jw, but eventually drifted off on his own in his early 20's.
He was ok with it and didn't blame me for anything. I honestly think it bothers me more than him. I know he would have liked to play team sports in high school.
Just be upfront about it and admit it was a mistake. Our experience with the JW's wasn't bad, just a case of lost opportunities.