All children will encounter the idea of God as they grow up. It runs through most classical literature and has shaped history. It is part of children's education to inform them of religion. I think that encouraging children to allow for the possibility that there to more in heaven and earth than can be presently known is a healthy outlook.
To allow room for the idea that there may be something greater than themselves that permeates the universe is sensible. A balanced view is likely to help children to feel secure. If they want to call that possibility God then that is as good a name as any. As they grow they will decide for themselves.
Indoctrination into a cult that causes children to live in fear is a very different matter.