I don't know if I've ever seen so many "likes" on a post so it is obviously excellent advice from coach2709. And as I was reading through Coach's post, I found myself nodding in total agreement all the way through before I saw the likes.
HOWEVER... as I think longer on this one, I actually disagree with the player handling this. I'm going to go against the grain with some of the folks who I respect the absolute most here on HSBBW.
I TOTALLY agree that dad stepping in on game day is the worst possible option. I totally agree that players this age need to handle their own business. But, look, the kids with the best attitudes, the kids who love to play the most, the kids who have been properly parented with respect to elders, those kids want to go where the coach tells them and have a good attitude about it. Those kids want to play instead of sit. Those kids want to be in the middle of things and it doesn't get any more "middle" than pitcher and catcher. Those kids want to help the team any way needed... and so on an so on. You get my point. So this is one topic where I find it appropriate for the parent to step in and say something like...
"Johnny would never say anything to you because he loves to play and wants to help the team wherever he is needed but we have studied up on how it is highly recommended not to have kids pitch and catch the same day unless it is just a few innings at each. He comes home and his legs are very tired from catching bullpens for two hours straight. Then he is asked to pitch and this is when, we're told, kids' mechanics will fail and arm injuries follow. We totally appreciate everything you do with the team and will stay out of all decisions you make but when it comes to any concerns with our son's health, we feel the need to communicate with you." "Are there maybe some reasonable guidelines that can be put in place with limits for pitching and catching?"
Then, when he asks what you had in mind, that's when you introduce him to HSBBW!!!!! Win, win, win 
JMO... any other issues regarding normal stuff, the kid handles it.