dial it back in front of the players/parents on both teams.
Respond to a comment, but don't initiate the conversation: "I'm very pleased he had a good outing." Big grins are always appropriate, though I recommend them mostly in the direction of your player. (Sometimes parents don't remember that the player pitched/hit/fielded well....all we did was watch well
)Teams can be tough on the opposite side of the fence, and empathy and foresight are important. For example, your son doing well represents a threat in PT for every other pitcher and (by extention) their parents. And every pitcher also has bad outings, which can be tougher to take if you've celebrated the good ones too much.
Old baseball saying --- don't let the highs be too high or the lows be too low ---- goes for parents, too!
Good luck to your player --- got lots of fun ahead!