Tons of great info given here already. I second what Midatlanticdad says... get some dialog from the school prior to the event. Ask some specific questions about where they may have seen you, what they like/don't like, what their interest level may be, etc. Between this and more feedback from your coach, you will get a much better idea of whether there is genuine interest or just another camp invite to generate $$.
It is usually a better sign of some specific interest when they go thru your coach vs sending you a mailer but we don't know specifics about what they emailed to your coach. Ask him.