So to further clarify this is a private party on a public forum?
NFA Day is open to all INGO members, with a cap on attendance. People were given a chance to sign up, and the attendees were picked from a random number generator.
Alumni Day is open to all INGO members who have previously attended an NFA Day.
The event is held on private property at a member's home range.
No different then your gunshot course.