Put it on plastic. Stuff about 4-6 bags of ice around it. Keep ice in bags so it doesn't water log the pig. Put a couple more on top/bottom, etc. Keep in shade, covered in plastic to keep bugs off.
Many times we very lightly pack with ice so it reaches room temp before hitting the grill. But, it being a work function, don't want to take any chances of it spoiling. 
This is how we do it in eastern NC.
Smoke and enjoy.
