Helo, I am an atheist in hiding.
I am married with 2 kids and love my wife very much. She is not a fundie but believes very strongly.
No she knows I am not a christian and I have never lied to her about my faith. I also have never fully expressed the degree of my lack of faith. She most often assumes it is ignorance on my part for not being christian.
But I have read the bible and have done more research on theism than she has. I just don't know of a way to talk about my lack of religion and talk about her's without insulting.
It is hard to address you lack of belief in a sky wizard in a rational manner without critisinsng another persons view of the sky wizard.
She has made no attempt to convert me nor would she.
I am simply concerned that with our 2 boys we will each express different conflicting views on the subject. I do not mind them being taught christian beliefs as it is important to under stand that the world we live in since much around us is christian. I fear teaching the athiest view point will not be as easy.
How do you teach the invisible sky wizard may not be real, with out criticizing the mother?
DISCLAIMER: I don't know crap about parenting, take my words at your own risk.
If religion were hot sauce, my parents would be the extra mild kind. How they decided to raise us was to not talk too much about what they believe, but say "some people believe this, some people believe that." I don't recall them ever talking about how they felt about it or even showing a preference. I would think this could work in your situation, where you and your wife avoid making any statements yourself, but simply state clearly what other people believe, and suggest that your children think about the possibilities themselves.
However, far more importantly than how you approach your children is that you and your wife fully understand each other. While I wouldn't normally tell someone to come out if they're not ready, when children enter the situation I personally think that is a signal that it's time to spill the beans whether you're ready or not. The longer you wait to tell her, the harder it is going to be and the less time you will have to discuss it together and come up with a solution that works for both of you.