I can't see how they could legally keep you from moving. You are their mother and they belong with you. But it depends on what kind of grandparents rights laws exist in KY. I wouldn't even bother talking to them. I would tell them you are moving because you can't deal with their abuse anymore.
"I came here tonight because when you realize you want to spend the rest of your life with somebody, you want the rest of your life to start as soon as possible." - Billy Crystal, When Harry met Sally