I guess I just don't see any need for a 7th grader to have a full time hitting coach. If he's hitting well, he's hitting well, and in most cases is only seeing pitching from kids his age or maybe a year older. Let him hit...until he's not hitting anymore....whether it's because he makes a change on his own, or he gets to HS and is facing guys potentially 3+ years older than him and needs to adjust to that level of pitching. What can a hitting coach tell you today that is different than what he told you last week or 3 weeks ago if your son is hitting well in game situations?
My son was very good hitter from the time he started playing travel at 10 years old. He had a very good coach at 12U that was a former MLB pitcher. He taught lessons part time at a facility owned by a former pro outfielder who also gave hitting lessons. We went to the hitting guy twice, once at 13U and once his freshman year....both times just a single one-hour session. Son had gotten into a funk and I could tell watching him that he was just thoroughly confused at the plate....and I had no idea how to fix it. Both times we went to the guy, he corrected a couple things he saw and things were back to normal.