Dear Waiting:
I was still agnostic when I married. That was 30 years ago.
Fortunately, neither my wife nor her parents are evangelical, although my wife, at least, is occasionally vocal regarding her faith.
In our 30 years of marriage, the only times my "atheism" has posed a problem for us is"
1) When some very significant life event happens that I cannot explain in scientific or physical terms to my wife or our two children, they try my lack of non-metaphysical explanation.
2) I have had some problems struggling with spiritual questions posed by my two children.
What I have found helpful is not to push my positions onto my wife or our children, and not to let anyone push anything on me. Arguments usually lead to taking firm stands, so I avoid them even though that may seem like a weakness to others who take a firmer stance in their atheism or anti-theism.
I also find it helpful to point out that my personal philosophy is based in iconoclasm rather than in trying to draw others away from their belief structure.
Good luck, and may you and your wife enjoy a long and happy marriage.
Peace.