Here are the guidelines from GC.com:
Event caches are gatherings that are open to all geocachers and which are
organized by geocachers. While a music concert, a garage sale, an organized
sporting event, a ham radio field day or a town's fireworks display might be
of interest to a large percentage of geocachers, such events are not
suitable for submission as event caches because the organizers and the
primary attendees are not geocachers. In addition, an event cache should not
be set up for the sole purpose of drawing together cachers for an organized
hunt of another cache or caches. Such group hunts are best organized using
the forums or an email distribution list.
Meet & greets can be set up as events, (that's right you can create an
event for the sole purpose of meeting cachers for food!) but a group cache
outing doesn't count.
Mike
