Treasure hunt party- invitations would be "weathered looking paper with a dashed line to the the X marks the spot. For the main party event use a large area (we have a church behind our house with several acres of space) and do a treasure hunt.  We are part of a relatively new sport called "geocaching" You use a GPS system To locate a coordinate (for more information go to www.geocaching.com) Enter several points into the system of locations where you have placed presents.  Have the child (At least 5 yrs old is recommended) take their friends on a REAL treasure hunt! The GPS will take you from point to point until you find the last present. This is a great family activity,too.