mifdaddy,
Not sure if many here have been to this event. I will try to answer your questions as honestly as possible. I definitely don't want to try to talk you into attending that event or any event.
I can’t tell you whether or not it is worth it. For some it surely is, for others maybe not.
I can say there will be no 2013 players in attendance. The top 2013s will be at the PG National also held at the Metrodome in Minneapolis. The Junior National is for underclassmen (2014 and younger).
I can’t tell you why your son was invited (don’t know who he is) but I can assure you that only highest level prospects have been invited, so we must consider him one. This is not an event for anyone who lacks talent. They would feel very much out of place.
I can honestly say that this event is heavily attended by top college programs from coast to coast. Last year well over 100 colleges and MLB scouts, mostly colleges attended. I think college recruiters consider this the premier event for underclassmen. I can say that the vast majority of kids that have attended this event ended up at DI colleges and/or drafted.
Maybe the best way to research the event is to go check out the past several Junior Nationals. You can go to this link....
PG JR NAT 2009 You will see the colleges those players committed to.
Here is the link for 2010
2010 JR NAT and here is the link from last year
2011 JR NATKeep in mind that these players were all just finishing their sophomore year or younger when they attended the Junior National. Maybe you will recognize someone listed and contact them for an opinion.