Fill cooler with ice, place a BBQ rack or such on top of the cooler while lid is open. Place fan on top of rack. Preferably a battery powered fan not electric, cause the water and all. Then pull cooler lid up to the fan, then add cardboard to insulate and control the cool air. Making sure to not cover up too much of the fans intake.
Step 2: Cooling Chair
Basic rolling computer chair, with cold compress strapped to the back, and umbrella attached to the chair... Works great when watching over yard sales and such.