James,
I understand what you're dealing with somewhat. I'm not sure the reason why you stay in is to teach your child morals because you could easily do that not being a JW. However, your leaving would have a dramtic impact on your family, right? What would happen to your marriage if you left?
Maybe I'm transferring my issues on to you but that's the thing that keeps me in. You have one son that is already out right? So you could have a frank conversation with him about why you no longer believe, apologize, etc. Depending on how old and what your relationship is with your other child, you may be able to have that same conversation. Is he/she baptized? If not, then your really can discourage that step.
How would your wife react? If she also has doubts, that may be an opportunity to leave with the only thing that really matters, your family.