A while ago when teaching in a primary school I had the class make a mobile of the planets and other celestial objects (star, moon, asteroid, sun etc.). The benefits of using this kind of approach are particularly apparent for visual and kinesthetic learners but in general for young learners it makes the experience of learning far more memorable and motivating. Of course the other advantage is that you can display the finished projects in the classroom afterwards for students to refer back to. The best thing to use is Polystyrene balls of various sizes which you can then have the students paint to represent the colour of each planet.