“But how?” they ask. “I need more information, father.” (These are very articulate children.)
If you want to tell them the truth, you can use this Danish book, which is very graphic.
But if you want to lie to them, you can use this video.
See? Daddy put mommy’s finger in his mouth and blew her up like a balloon. And then, out popped the baby! Like magic!
By the way, I’m kidding about the “lie to your kids” thing. The video, by Cassidy Curtis and Raquel Coelho, does not suggest that you should lie to your kids about where babies come from. It’s just a funny video. Well done.