The answer really depends on whether the parents are religious. Religious parents, particularly Christian ones, generally believe that religion is very important in a child's development. There was a saint (I forget which) who said "Give the me child for his first seven years, and I will give you the man." The reason most frequently given is that religion instills particular values in children at an early age. There are other considerations as well, such as in Judaism, many traditions (Passover seders, Hannukah celebrations) while religious ini origin, have become more secular events that are celebrated by the less-religious as well.
The flip side is that atheists and other freethinkers generally feel that religion is harmful to a child's development. Many hold that children are incapable of thinking deeply enough about religious questions and to impose religious beliefs on young children especially forces them into roles in which they don't fully understand. For example, one often speaks of a Jewish or Muslim child, but we would never dream of referring to a child as, say, a Republican or Democratic child. As parents, our values tend to rub off on our children, but, at least with political beliefs, most parents allow their children to make up their own minds, and most atheists belive it should be the same with religion.
Further along the spectrum would be those who believe that ANY belief in the supernatural imposed on children does them harm. In the interest of full disclosure, I fall into this last category.