Hide a chest full of loot in the snow, then watch young castaways track it down clue by clue.
Look around the yard for good clue hiding places and plot them on paper. Then create the picture clues for each spot and hide them in order (keep the master list just in case a clue gets lost).
For more sophisticated castaways, give them their clues in riddles or use rebuses.
Pack a cooler full of treats and then hide the "treasure chest."
Create a series of clues leading to the chest. Use either pictures from magazines or create your own with markers and paper.
Place each clue in a plastic bag and hide it in the snow.
Begin the hunt by handing the players their first clue.