Golden $1 coin treasure hunt birthday party

Most ingenious + sneakily thrifty child's birthday we've ever been to involved a collaborative backyard treasure hunt for a hoard of golden coins that turned out to be REAL money (cannily, the treasure could be split evenly and exactly among the kids, two coins each). Everyone got another golden dollar as a favor. The kids were thrilled and the parents were envious b/c it cost about $30 for ten kids (plus pizza and cake), involved zero rentals, kept everyone occupied for over an hour, and did not involve foisting bags of candy/plastic on all and sundry. We now give golden dollar coins as gifts; always a hit, esp. with young treasure-hunters.