you can find many bodyweight exercises here http://homegym-exercises.com/gluteal_muscles_and_buttocks_bodyweight_training_without_weights.html
That's what I was thinking. He'll have to do like 4 sets of 100 There are good upper body exercises like pull ups and chin ups but it's harder for lower body ones
Seated leg press is good for the calves. Instead of a full quad press, simply bend your knees slightly and push on the platform with only your toes. 5 sets of 20-25 on a heavy-ish weight will tone and build fine calf muscles.
Squat jumps lunges calf raises wall sits. If its too easy try one legged. If its hard to balance stand next to a wall