Scouts are given grid references, maps and compasses and use these to find the easter eggs.
maps, easter eggs, prepare grid references with clues, (compasses optional)
before the meeting hide easter egg/s if on regularly used public land hide fairly well but give a clue e.g. if hiding an egg under a bridge put where the troll lives etc.
Each patrol is given their grid reference these can be to different eggs or if you want to encourage competition to the same one either just give it to them on run a quiz/game and each time they win/answer correctly they get a number of the grid reference.
Scouts then have to work out the location of their easter egg on their map and go and get it.