COVERTS- Man, I really feel for you bro. When I started having doubts about JW's in my first marriage with my JW wife , my kids were 13, 11, and 10 , a little older than your kids , but not much. We separated not long after that. Then divorced. As others have said here- there is no easy way to play the pretend game. First off- it's unhealthy physically & emotionally on you, your mate, and our kids are smarter than we think- they can feel the tension in the family atmosphere.
That being said if you are hoping to stay with your wife and kids for the long haul , I suggest not discussing any JW topic with your wife or your wife's family. Anything you say can or will be used against you by the " court of judicial committee's " if you get my drift. I know one thing some folks have done on the board here is follow Steve Hassan's advice ( he's a cult exit counselor ) when we are stuck in a family of cult members and they take time to do lots of activities away from the kingdom hall with the family. Activities that have nothing to do with JW's, WT, or anything religious.
For instance - ask yourself, what hobbies or activities does your wife enjoy doing that has nothing to do with the Witnesses ? Does she enjoy shopping ? Going to movies ? Bicycling, walking, going to parks or nature walks with you and the kids ? Do either of you like music ? Going to an outdoor concert ? Even growing a vegetable garden in the back yard ? I'm grasping at straws here- but you get the point. Any activity that you can engage in with them that will take up your wife or your children's time and get them into thinking in terms of reality in the here and now can be a positive influence to their too narrow JW world views. It gets their mind thinking on other things than only JW things.
Just a suggestion buddy. Some have tried this and it has helped. All the while telling your wife and kids you love them and that you enjoy doing these things with them. If your wife is a hardcore JW , it probably won't get her out of the cult- but it will help make your existence and your relationship with her and the kids easier than just looking at it as a " good guy / bad guy " situation. You and your family could actually have some bonding doing non-JW activities ! Isn't that a hell of a concept ! ? lol.
I wish you the best of luck. If you ever want to chat, just PM me, I'd be glad to talk sometime with you