I want to emphasize what everyone said about critical thinking skills and being a good parent. I have been DFed for about 5 years, my children are teenager and almost teenager. I focused at first on being a good parent. When they were worried that I was going to die at Armageddon I simply said "I'm not going anywhere for now, let's deal with that when Armageddon comes."
I took them to movies, made sure that at least on either Saturday or Sunday morning, instead of service and meetings, we went out for a pancake breakfast or to the park or on a hike, something fun but always wasn't "bad" in the JW eyes.
I also let them watch a few things they couldn't in their father's JW house, letting them know I had no problem with it and when they are at my house, I have my rules and their father has his BUT that doesn't mean they run wild and do whatever they want.
I also taught them critical thinking, a love of science and learning and how to play the "what is more likely" game. We used critical thinking figure out why other religions are crackpots and slowly applied that to Bible in general. Once we were at that point, the bottom fell out for any hope their father had of them being JWs.
They've seen LoTR, The Hobbit, Nightmare Before Christmas, The Walking Dead, have had and been to birthday parties, etc.
Remove the fear JWs instill and replace it with love and knowledge.