The problem with trying to free individuals, and both your sons are different, is that a trigger that may work with one person will have no effect on another.
When you read the threads on here as to why and how people woke up there are so many varied reasons,when I look back on my own experience there were many things I was aware of, that were enough to awaken others, but not dumb old me,until my "trigger" came along.
What I am leading up to is: if you wish to free your sons , you may do more harm than good by pushing various issues under their noses, they may come to view you as trying to do exactly what you are trying to do, get them to leave the religion, they will then cease to listen.
Having said that, I am not sure of the best approach, but something that comes to mind is try first of all to simply ask "what convinces you it is the truth ?"
They know you have "doubts" so you can say their reason for their faith may help you restore yours.
The answers will give you a clue as to what their belief really stands upon, will also make them look at their faith.
Do not attack their reasons in any way, or even comment on them, just thank them , and then ask, "But you know many folks have problems with various things about the JW's, surely to you, not everything is perfect about the religion ?"
You can then agree 100% with any problem they highlight, and point out how, if it were God's org. surely such a problem should not exist within it ?
All you may achieve by this is getting tham to think a little, but that is a good start, and you should not alienate them.
Keep assuring them of your unconditional love.
Just my thoughts, and the best of luck !