In your place, I wouldn't get involved at all in the details of your W's affair. There is no upside for you or your kids other than to make your W look like a fool. She is doing a fine job of that without any help from you. You will just look like a spiteful XH.
Document the behaviors of your wife's BF. Your kids should never go near a car he is driving. If he has unhealthy habits, you may be able to legally limit your kids exposure to him.
