This might get move to IMHO, cause each of us will do this his/her own way…
I am not actively atheist so much as areligious/agnostic, but we just never really bring up religion. We do celebrate some “religious” holidays as cultural events, like Christmas, St. Nicholastag and Easter. When we lived in Thailand, my daughter had a neighbor friend tell her about God. Since we’d never discussed the concept, she heard this as “Guard” (there are a lot of security guards around the complex where we lived there). One day she told me she believed in “Guard”. I tried to correct this to God, but thought it was kind of funny and fitting. “Guard watches us and makes sure nothing bad happens to us”, she told me in earnest. Can’t really argue with logic like that.
More recently, as we’ve moved back to the US, our kids have been more expose to more active discussions of religion and beliefs, both on the street and in school. When she asks I explain to her what different people believe. I don’t disparage anyone’s beliefs to her just as I wouldn’t disparage someone’s beliefs to them. FTR I also have a son and this discussion has not come up with him. He believes in Batman (okay, he knows Batman is not a real person, but he still has a sort of hero worship there).