I took my 6 year old to the Hayden Planetarium they day after "resurrection Sunday." In the days before our trip, she explained to me that "scientists don't know if the universe goes on for infinity or ends or if there are lots of different universes."
She told me that she wants to be the one who finds out the true answer when she grows up.
During our visit to the planetarium, she became somewhat concerned about what was there before the Big Bang. She said she might discover the answer to that question too when she grows up.
Kids really like to have the answer to questions. And almost any answer will satisfy them. The little 5 year old who accepted Jesus and wants to tell people about god is not that different from my little girl. If I told my little girl that crystal fairies created the universe in 4 hours, and that the universe was shaped like a piece of rock candy, she would have been satisfied.
She still wants THE ANSWERS, and is a little impatient with the scientists who don't have all the answers yet. But I have explained to her that science takes time, and that scientists today know a whole lot more than they did when I was a little girl. And for her, this is motivation to learn and discover.