I left the JWs when my kids were about 12 and 14 I think, but they had been raised as JWs their entire lives and believed it was true. We were the perfect JW family and my husband is an elder. I was afraid I'd lost them already.
When I started to have doubts about the JW religion, I didn't say anything to my kids, but when I became sure that they were wrong, I started talking to them, asking them questions and encouraged them to tell me what they thought. That was hard, at their age, because they had already learned that you don't question the WTS teachings, and they were very hesitant. But once they did start talking, the floodgates opened.
I'd say that the most important thing you can do is to keep the lines of communication open with your kids. They need to know that no matter what they believe or don't believe, you will love them unconditionally. Your kids are young enough that you have time to lay a great foundation with them. If they believe that no matter what happens, you have their best interests at heart and love them, they will listen to what you say, even if it goes against what they learn at the meetings.
Do NOT let them get baptized. If your wife is a balanced JW, then appeal to her before this even becomes an issue. Point out the lunacy of 6 year olds getting baptized and making a lifelong comittment to something they have no capacity to even understand fully. Tell her that if your kids decide to get baptized (this is purely hypothetical, mind you, to pacify your wife), that you want them to be able to make a meaningful dedication and understand what they're doing, and that can't happen until they are much older.
If you can keep them away from meetings, that's still the best option imho. But I know that's not always feasable. Even if you do keep them away from meetings, you still need to have a great relationship with them and keep communicating and accepting them for who they are. Unconditional love is a basic human need, and the WTS comes up way short in that department.
Good luck to you.
GGG