While standballdad is correct, I will provide you with a little more info from MY perspective.
When a kid should attend a PG Showcase is not something you can predict when they are 11. There are certain levels, for some they are more like hurdles, that kids must get exposed to and cross before a showcase like that comes into play.
So when will you know when to take him? My advice, let him just play for now. If school allows it let him get lots and lots of extra reps. Training is also fine. The more he learns how to do things correctly right now, the less has to be corrected later. Over time, should he continue to play, he will be exposed to better baseball. The teams and their players will be much better. By the time he is 14 you will start, should you not be one of those dads that wears rose colored glasses, to understand where he fits in. At that point you can decide.
My son is a HS sophomore, just turned 15 in August, and he just attended his first PG Showcase. You have to understand that the skills portion is just that, not very complicated. But the games, should your son not be ready to face kids throwing 85+, are something that may make you stop and reevaluate things.
A day at a time. He's too young right now to plan that far out in advance.