Here are some movements that I feel would be a good start for a young ball player. It’s imperative that he learn the proper technique for all of these, which generally takes some time. So I will assume you or a certified trainer knows these movements.
Air squats, broad jumps, box jumps, standard burpees, Beck’s burpees, walking lunges, push ups, tuck jumps, sit ups.
Ball clean (use a basketball or soccerball).
Unloaded power cleans and snatches, unloaded thrusters, unloaded press and push press (use pvc).
Very light weight deadlifts (use a light kettlebell or some similar lightweight object).
Pull ups (begin with progressions and work over a long time to achieve a strict and then kipping pull up)
Sprints
Light weight sled dragging and pushing
Light tire flips/spartans (once he consistently demonstrates proper deadlift form)
Object throwing (eg, max effort basketball chest passes or backward, ie, flinging over his head, underhand throws)
Wheel barrow walks
Handstands, cartwheels
Again, it’s extremely important that your son moves well with these exercises before getting involved in any kind of high-intensity, coach-driven workouts. That doesn’t mean you can’t introduce these movements to him, then mix and match them to create a WOD that he can do. Just monitor and correct his form and allow him to govern his intensity level.
An example WOD at the ball field might be this:
Sprint home to first base (run through the bag properly), do 10 air squats, return home.
Sprint home to second (slide properly into the bag), do 5 lunges with each leg, return home.
Sprint home to third (slide into the bag), do 5 burpees, return home.
Sprint a homerun (slide into home), do five push ups.
He governs the intensity of the sprint, you monitor his movements and cue proper form.