Give a prize to the first done and also the last. As mentioned above a prize for all is always a good idea. A nice set of Thank You Notes, Pencils, Pens, Crayons, Markers, Stationary or even some Crossword Puzzle Books would be a cute prize idea. Allow ten minutes for the hunt. At the end of that time guests stop hunting and count their turkeys.
Prizes are the cookies they found.
If the weather is nice you can do this outside too. If you have time or want to keep the kids busy then give them all baskets to collect them in and put out a large amount for them to find. The miniature pumpkins and harvest colored corn can be substituted for the cookies. Each player in turn must carry a spoonful of cranberries from the front of the line to a given point and back, then hand the spoon to the next player in line. If any of the cranberries drop off, the player must stop and replace them before continuing.