I read a while ago about a theory that was quite interesting..
With God being infinitely amazing at everything, there was no point in doing anything. The only thing that seemed challenging for almighty God was.. 'To destroy Himself!'
So he took on this challenge and the result was the big bang.
Turns out it is impossible to destroy God, even by God himself, so his shattered remains are our universe. (Replace God with energy?)
Now this theory predicts that the universe and everything that makes it is turning back into one God again over the entirety of time.
With the way networking and discoveries are advancing, this story fits quite nicely and is simple enough to tell the children.