I think at those ages, less is often(usually?) more. Are they in Rec pro’grums? Travel? IF travel, how many times/week/month are they doing high(er) stress throws, e.g. pitching, playing catcher, etc.?
Is the 11 y/o advanced physically? As in, my 11 y/o has a coupla 12 y/o on his LL team that...