Your situation is not an easy one. It's clear that you care about your kids a great deal and want to have a good relationship with them. It's best to not try too hard to control things. If your kids choose to be JW's, it's best to just let them be and make sure they understand that you're there for them no matter what they believe. When you are with your children, it's best to appear to be happy even if you're really feeling down. Kids don't remember everything you say, but they do remember how you made them feel.
Someone else suggested hiring an attorney who has some understanding of how JW's operate. You may need to educate your attorney about what you're up against. No matter what you tell him/her, or anyone else, put it in writing as well. It's only when things are written down that the arguments over who-said-what can be shown accurately. People are forgetful as well, and misconstrue things you say. So, write it down.
Meanwhile, go on with your life. Decide what you want to do, set goals, and take steps toward living the life you want for yourself.
Best wishes,
Mum