I don't have experience with this event, but from experience I can tell you PG runs very organized events. What is your motivation to go? The rating? Does he have measurable's that will get attention? How big is he? How hard does he throw? How good of a student is he?
What are his target schools? I'd be thinking about events where some of those colleges are attending. Also, it could make more sense to hold off for a PG Sunshine or Academic showcase in May or early June. He could get ranked there, then, if he did well he could get invited to the PG National showcase. More exposure opportunities... A lot of colleges throughout the nation attend these events. Could be better bang for the buck.
Has he communicated much with any schools? Any interest?
Not answering your questions, but it's all related so that you can develop a recruiting plan and timeline to increase probability for your son.