Here’s a quick idea to help students visualise how the Moon and Earth move relative to the Sun. It can be quite hard for children to understand their motion relative to each other, so a real model that they can move may help them to grasp the idea.
You can download a template for the Sun, Earth, Moon Model here. Print the sheet, cut all the shapes out, and use split pins to hold everything together.
You can of course also use computer simulations to help model this as well. A good example includes this one from BBC Bitesize (needs Flash).
For motion of all the planets, do check out Solar System Scope, which remains one of my favourites.