AUSSIE OZ- Wow ! Great advice by EVERYBODY on this thread ! We have such awesome posters on this board !
I'll approach something from my own experience and something Nugget touched on in her comment when she stated " It is entirely likely that your ex-wife has already said quite a lot to them about the breakup and they may already know some of what happened but not necessarily the why . " Very good statement.
But wrap your mind around this : Your children understand the WHY of your breakup- ONLY from your JW ex-wife's vantage point. My JW ex-wife was WAY too detailed in describing intimate details of our sex life to my teenage daughters - lying to them that I had forced her to let me service her orally thus she turned me into the elders. And that is NOT how it went down at all ! She was a willing participant ! She dishonestly misrepresented me to my daughters to make herself look better and me look like a dog.
If your wife has any influence on your kids as a JW mom and is the slightest bit manipulative take what I'm saying to heart. I've been here, paid the debt my friend. And it is HELL trying to undo what a manipulative JW ex-wife can do in influencing your children against you. I would just privately talk with your children and perhaps ask first - " What do you know about mom & my breakup ? " Get THEIR opinion first. THEN you will know what they've been told and what kind of corrections you may need to make in access to information they have heard.
I don't know if you are closer to your kids than your ex-wife, but my older son and I are VERY close, he saw through his mom's BS. My girls not so much because they are mind controlled by the cult. You are going to need to be a psychologist to do this carefully keeping your relationship intact. But I agree with others- don't expose too much detail on your blunders about sex. Teens don't want to hear it. Good luck