My Cakies has a really cute idea for a scavenger hunt kit. One variation can be to eliminate the camera and instead ask for objects which can be taped to the pages. Although the camera is great for memories, it's not ideal for a large group or if you don't have a Polaroid.
Good for ages 4 and up.
Get the instructions here:
http://mycakies.blogspot.com/2011/06/oh-hunting-we-will-go-papi-day-surprise.html
Scavenger hunt fun shares several ways for how to create a scavenger hunt including cutting up pictures of the items and having the kids put them together to reveal the clue, picture puzzles, rhymes, secret codes, and trivia.
Get the instructions here:
http://www.scavenger-hunt-fun.com/scavenger-hunt-clues.html