The report Sustainable Demographic Dividend shows that overall and especially in the United States, religious people have more kids than secular people. In the 53 rich countries they surveyed, religious people have a 2.21 birthrate, while secular people have a birthrate of 1.69 — not enough to replace themselves.
Now it's true that many children of religious people don't keep the faith.
But just remember they don't all have to.
The interesting thing is that it makes religious views normal. A youngster might not agree that abortion is murder, but he's more likely to accept that there are other points of view in the world, other than his own.