i've worked with young athletes for a few years, i'd have to say world's strongest man style training is very beneficial.
here's what i mean, have them pick up a 20 to 40 pound sac, carry it 15 yards and then back, have them go through an obstacle course where they have to push weighted apparatus' around, have them do light farmer's walks (forces the core to stabilize as well as putting direct stress on tendon and ligament inserts). backward sled drags are great too. focus on core stability first, then work out from there. good luck.
p.s. plyometrics are a very bad idea, very bad. 10 year olds do not have the ability to generate a stretch reflex that is able to stabilize the working joints and still cause an explosive movement. shy away from them till the athletes can handle 1 and 1/2 times there bodyweight in compound lifts like the squat and deadlift.