Call me old fashioned but I think this is too young an age (3 - 5) to go into such detail about unborn babies. Let them be children!!
I think it's the perfect age. It's really more of a story about where they were before they were born, than about abortion. Little children love that!
When I was about that age, LIFE Magazine had published a photographic essay of life from conception to birth and my parents let me look at that magazine. It was certainly as graphic as this story but I think it was good for me to read.