Pace out the solar system over half a mile, to scale
Print out of planets, instruction sheet, cones or markers, tape or blutac, half mile footpath or field
print out the planets sheet, on a sheet of A4 paper they should be to scale. Cut to separate them. Use a football as the sun. Pace out to mercury, use a cone to mark the distance and stick the planet to the cone with tape. Pace and mark each planet, and you will see how big the distances are between them.