There is campfire tool and shelter icons at the end of the camp names'
You can check if you did the maintenance in that area while looking at the tool section has a green check mark.

You need to give the camper 10 gold to start the mission and camper gives you a clue for the treasure. Camper is a bunny named Chen at Willows Beach.

You can find the treasure by clicking the rock at the Willows Creek. There is an island shaped like a hand.