One way to introduce children to Astronomy, is this one:
Fix planets on the ceiling of the room like you have seen. This is the Solar System, with the Sun just above his head and the rest of the planets going to the door...
The nice thing is that the planets have a dim bright at night, so, it helps to remove fear to darkness and it is showing him one nice topic, Astronomy. My child asked the names of the planets... after a couple of days of repeating them, he is already remembering them! Also it's a good memory exercise!
And yes... I consider Pluto as one member of the Solar System, but I'd also put Charon as they share the rotation orbit centre between them.
Sorry for earth-flat believers.. I'm not one of yours... ;)