In order for children to decide what they want to believe in, they have to have
knowledge first. I don't believe in God either, despite my catholic upbringing - or should I say because
of my catholic background.
My child went to a catholic school until she was old enough to question their
religion and she has made up her mind that she won't believe in God (she's 14 years old). I did not influence her decision and I would not have if she had
decided to believe in God.
Don't base your wish to have children on the absence of a religious belief.