At about your son's age we got something called a "hit-a-way" that we tied to the basketball goal so he could practice on his own. Son is a righty, but he started hitting left on his own terms, just playing around. It helped hand-eye coordination and dad didn't always have to take him to the field to hit. Something like this:
http://www.dickssportinggoods....16slzuhtwybsbllxxtra
Son wound up being a switch hitter in high school and college