I have been an atheist since I was 12. DH is catholic, and when we met 13 yrs ago he was a regular churchgoer although hasn't been for the last 6 years or so because of the child abuse scandal. We got married in church, but only because he told me that if we didn't, we wouldn't get married at all. I went along with it because I knew it was important to him, but equally he knew my views.
Anyway, we were out for a meal last night, and I mentioned that DC, 7 & 9 had asked me about a book beside my bed. The Portable Atheist (which incidentally, DH bought for me). They asked me what it meant, and I explained that not all people believe in God, and even those that do, some believe in different Gods. They asked me a direct question if I believed in god, and I answered no, but I believed that some of the things in the bible May have happened and that people's scientific understanding at the time meant that they thought god had done things. We discussed Noah as an example. We talked about how it was fine to believe different things to other people and to respect other peoples views.
I didn't think it was a big issue, in fact I think it healthy that they know there is a different viewpoint. When I mentioned it to DH, he cracked up. He thinks that there is a risk that our DC will grow up not knowing about morality and won't know right from wrong.
An argument followed, where I told him I thought it was ridiculous to suggest that Christian teaching had sole preserve over morality, and that the child abuse that has occurred clearly demonstrated that it hadn't worked in practice.
We spent the rest of the meal in silence. Tbh this is part of a bigger issue with DH at the moment. He is stressed with work, and has been really argumentative and unpleasant to be around. I honestly think that the bigger risk to our DC is seeing his toxic behaviour at the moment, rather than knowing that some people don't believe in god. I just need to vent.