This reply is meant to suggest some thought on the subject, not necessarily to say " don't do it."
The players in the professional game are fully developed men who have gone through an experience called the Minor Leagues. Their bodies are toned and have endured stamina and tolerances that one can only experience by being there.
Youngsters in this game are still going through growing spurts, mental a other maturity issues that is as individual and personal as it gets.
I would suggest watching your charges and using your experience and expertise, tailor the advantages of each player.
You'll notice, I'm sure, that the tall slender player has unique characters over and above the stocky players, and yet those that are athletic compared to those still in the rookie stages. Language also plays an important role with player development. Some may not have the language of the game fully understood, and some may walk on your field expecting to learn from scratch.
The amateur youth game in baseball is dynamic as it challenging. You've really got your work cut out for you. Nine plus players, all looking to you for their individual success story is a daunting task, to say the least.