M.L.
What sort of things does your son love to do? Can you surprise him by arranging for him and a few of his friends to do that thing? Or... I remember a surprise party for a friend of my son, in which the boy's parents arranged for his friends to surprise him at 7 a.m. by showing up - in a limo - to take him to breakfast before school. You'd be surprised how quickly a teenage boy will get up and dress when his buddies are there in a limo. If you don't know where to start, take your son's best friend into your confidence and ask him. He'll be the expert.