Well if it matters I use the radar gun on all pitchers. That way when I see an opposing pitcher throwing 70 mph I can tell my son on the batting circle to be very patient and scoot up toward the pitcher. I also can identify when fatigue sets in with my son.
It's real embarrassing when I yell "Scoot up toward the pitcher" in a game. 
It's also real fun when I'm wearing a D1 University baseball cap and have my gun out.
What are you going to do if your son is lucky enough to play at the next level(s)? You going to follow him around with your radar gun to tell him what to do at the plate every game he plays in college, minor leagues or pros?
Why not let him learn to do this on his own?
Let him learn to tell a coach when his gas tank is running empty in order to take him out?
I don't know.
No
Ok
Yes