it depends on what you guys like, like coach c bove says be cautious with your son, these workouts are intense.
if you like things involving sports trainings, like football drills, basketball drills, soccer drills, etc, all mixed in with cardio and muscle exercises then insanity is for you.
if you like workouts that involve diffirent forms of fighting, kickboxing, mma, etc to real music then i would go with combat.
if you only care about how many calories burned, i hear les mills combat burns high hundreds to thousands of calories where as insanity burns calories in the mid to high hundreds. either one you choose itll be a good choice.
if you pick les mills pre order it by the 3rd for free shipping, and order through a coach site or team beachbody for bonus dvds.
Order Insanity or Les Mills Combat HERE