Word of advice. Make sure your agreement comes with an understanding that they will put him on their roster. We played several tournaments and son was never added to roster. His play still drew interest from scouts watching but he did not get credit on PG site for any of it.
PG message board is the easiest but you have to know what age and what events you want to play in. Don't be ashamed to play him up because several teams are always looking for pitchers. You should not have to pay to be a guest PO other than maybe a few dollars if they let you keep jersey. Other than that they are normally the ones needing players so we never paid to play as a guest with any of my sons.