"the idea of being raised as child without any explanations about the world or comforts to be held, scares me."
What a strange thing to say. What makes you think atheists do this? I tell my children what we know about the world, and what we don't yet know. No need to make up anything short of Santa and the Tooth Fairy, but they grow out of this fast.
"Also, on the opposite of the spectrum, what happens when your child converts(?)"
I can only speak for myself, not atheists, but my kids are encouraged to make up their own minds. I take every opportunity to discuss religion and my kids even go to a catholic school. I consider it essential to understand history art and culture.
That said, they are very comfortable with atheism and they don't find any of religion comforting, quite the opposite. It's disturbing to them.