Dialed, Absorber is right.. those there evaluating players could care less about the umpiring. If it's a clown show, they may get a brief chuckle out of it but that is not what they are looking at at all. They may be somewhat interested in seeing a player reaction to a really bad call but they sure don't care about the bad calls or anything to do with the umpiring.
It is definitely not my experience that there are not sufficient PG personnel at PG Showcases but I think they may have started to offer events to younger age groups since we were immersed. How old is your son and what was the event?