It's just an idea, which came to my mind.  I think, that christianic God can be quite well compared to Santa Claus. Let me explain why.
Santa Claus is a person based on an European tradition, brought to America. He originates from Dutch (and maybe German) character, Sinterklass. Sinterklass and other similar characters, like british Father Christmas, all originate from one real person. There was a man in area of Greece (today Turkey territory), called Nicholas of Myra. He had a talent of settling up conflicts and helping others, and he was promoted to a  bishop. He was also known for his secret gifts, which also helped many people. Legends about him became the basis of mythical gift-giving men in various cultures.

And now have a look, what is the difference between the fat, red, white-bearded, north pole inhabitating, Coca Cola selling Santa Claus, and a greece priest Nikolaos. Nicholas existed, Santa is just a tale, and doesn't resemble the bishop much, just in details (like a gift in a stocking, for example).
The same thing is with the christianic God. Whatever it was when it communicated with chosen people, guided a chosen nation, and actively participated on, for example, their wars, it didn't require a faith in the fact of existence of God (it was obvious), but that this one God is the only true god (there was more of them, and not only statues). People of the chosen nation had their proof of God's existence, witnessing "miracles" of a water source location, lightning control, smoke and fire pillars guiding them, unknown, massive flying objects, and so on. ("...and the book flew through an air" - note, that "book" in these times was a scroll, this is a description of a flying object of a cyllindric shape)
The christianic idea of God is a compilate of above mentioned characteristics and other sources, it doesn't describe the original God(s) more precisely than Santa Claus resembles St. Nikolaos. But it existed, though differently than we think today. The belief in God has a real basis, just like a belief in Santa Claus. There's a huge difference between the truth and today's legendary version, so we should put a critical, historical look on christianic God, just like we did on a Santa Claus tale. (though there can be some quite unbelievable old-new discoveries)
I think we can just tell children why and how Santa Claus appeared, and they will understand it. Similarly we can describe a meaning of the God idea, using a simile of the above mentioned. There is no need to make them blindly believe that Santa Claus and christianic God exists exactly as media or religion tells them.

I'm sorry if it will appear in weird colors (like all white) but this is, how this text editor behaves today, whatever I do.