An evening of basic mapwork, gridreferences and orienteering
Enlarged OS map of area (laminated), list of Grid references, Glowsticks, Walkie Talkies, head lamps, compass
Give each group an enlarged OS map of the area showing them where they are and how to set the map to north. Give the group(s) a grid reference of a pre-hidden marker (in this case glowsticks, as activity being carried out in the dark) The group has to work out the grid reference and how to get to the location, once there they find the marker and you give them the next one. The activity continues in a loop until either the end of the meeting or they find all markers. For the uninitiated plan for them to not complete all of the activity but have a few extra ready if you think your group might be very good at grid refences. Make the activity suit your time and area available, you could use different makers in the day time or for older sections get them to actually plan their route before hand around the area telling them they have to visit each marker.