The most important thing you can do for your pup once he's jabbed is socialisation, number 1, forget bout exercise, at that age he'll exercise himself, running round playing with things,
Get him out with people , traffic, other animals, travel him in the car, break him to cats, walk him through town , people will make a fuss of him, its all part of his development
Because by the time he's 16/17 weeks, the fear factor kicks in, thats when a pup starts looking at the world through fear tinted glasses, effectively he evolves a consciousness where he understands he could be prey for something bi