Your children have been indicated into a cult, that took time, it will take time to unindoctrinate. Ask them questions to help then learn to look at things differently. You could ask " Do you think God is loving" . If they say yes, then ask " Do you think a loving God would kill innocent children?". Then just leave it, let them think about that for a while. There are so many logical fallacies to the JW belief system, even children can see it if it is presented in the right way.
Another time you could say "If God exists......" That way you can plant the idea that there is a possibility that he actually doesn't exist. If they say they are afraid for you, just reassure them that you are doing what you think is right, that there are many opinions about God and whether he exists or not, and if he does exist there are different opinions about what he wants. Eventually they will start to accept your choice even if they don't agree. As they get older they will naturally start to think more for them selves, that just normal human development. Then the seeds you have planted will take root and grow. It will be a lot easier for them if the know at least one parent supports them if they choose not to be Jehovah's Witnesses.
Very often children are believers in early childhood, up until they hit puberty, then they start to think more independently and have questions and doubts. The retention rate for JW children is quite low, so obviously many children reject the religion, that's why it is such a tragedy that so many get baptized at a young age, they are still just reflecting the religion of their parents, it's not a mature decision. Just be there for your kids and help them adjust when that does happen.