pity that you can't be moral without fear of reprisal in the afterlife
I think attempting to control behavior by evoking fear of reprisal in the afterlife is one of utter futility when dealing with kids. Who among us has never sinned using whatever criteria we have been taught to identify sin? And once you're headed for hell anyway, you don't have much to lose.
In my decades of observing the phenomenon though, I am convinced that those who reject a rigid fundamentalist religion tend to reject all of it and become sometimes antisocially rebellious. Or, if they reject it, they just go through the motons later on without any conviction behind it.
Those raised in faiths in which the basics are taught but independent questions and thought and logic and reason are encouraged are much more likely to stay with it their entire lives and encourage their children to follow suit.
It is a fact that children on average who grow up in the church are more likely to graduate highschool, obtain at least some higher learning, stay out of serious trouble, and achieve a degree of success in life. That is not to say that all will or that no children raised as Atheists will likely succeed.
But you don't wait until they are old enough to decide for themselves before exposing them to reading, writing, arithmetic, science, social studies, music, arts, sports, or anything else that might be important in their life. And yet each kid, exposed to these things, grows up with his/her own unique interests and focus.
Why would you wait to give a child opportunity to learn about something as important as religious faith?