It can be very hard to visualise just how big the solar system really is, so putting it in the context of their local area can help the children to grasp the scale. This handy little website by Keith Enevoldsen allows you to place a scale model of the solar system on a Google map.
You may have already made a scale model in your school grounds, this version takes it a step further. Choose a size for the sun (eg 1m across) and then pick a location. The website then does the rest.
You might find that the site can’t find your location, in which case try this site to help you find out your latitude and longitude to enter manually.