Take a flying visit through the Solar System, taking trips in relative distances to all the major elements (8 planets, Asteroid Belt & Pluto)
Relative scale of Planet distances to area - the bigger the area the better! (http://thinkzone.wlonk.com/SS/SolarSystemModel.php calculates this for you)
After (optionally) donning suitable Space Exploration gear (miming obviously!), start at the sun, take as many steps as required to move to the next object, getting Young Person to guess how far to go and answer which the next object is using clues or their prior knowledge. Once at the limit, fly back through the Solar system noting what we fly past. Turn around and name objects and get the YP to run to where the object should be, before "flying" to the actual location.