I agree with ST about giving the young man plenty to do.  If you and his dad can avoid micro-managing his efforts he will have a good time.  Not giving him stuff to do may lead to his being bored.  Tell his Dad to let him bring the Game Boy along...
I also agree that leaving Dad and Son to themselves a good share of the time will enable them to enjoy each other's company.  My husband and son always got along much better when I wasn't around complicating things.
I have found that youngsters have as good a time or even more fun than the adults on wilderness trips.  It may take a day or two for the young man to get over not turning on the computer or TV when he wants something to do; but once he does he should be a happy camper.