If you are talking about disclosure in a divorce action it is best to err on the side of full disclosure so as to not have any agreement attacked later on and set aside.  I am a little confused about this policy that you hold and everything that has been going on but it really is an aside to the real issue here.  Now, you may not be required to continue to pay health insurance for your soon to be ex husband after the divorce and most definintaely may not be required for his children as you will no longer be their step-mother.  There will be no legal relationship there.  I am hoping that you are going in to the mediation with an attorney to help you with this and you should double check with him or her on this issue.  Good luck.