I love democracy.
For one desenting vote so far. I do and have had my kids lift.( I dont see the difference between doing Light bench press and pushups especilly if the the weight is much less than body weight)
They work legs and rotator cuff stuff which are well outlined in other places.
They dont do these prior to a practice or a game and the weights for my nine year old are light with 10 to 15 reps per set, one to two sets per session.
Because the Rotator cuff is such a hard muscle group to exercise and isolate, weights become almost a neccessity to help prevent injury there.
Ther is good documentation such as the Mayo clinic, ASMI and other organizations that indicate that weight training with light weight is a signifigant benifit for children 8yrs and above for all types of athletic endeavors.
The critical issue is that at NO time should maximal or anything approaching maximal lifts should be attempted.
Reps, reps, reps.
Rollerman