How about a national gathering of people who, as infants, played the role of the baby Jesus in long-ago Christmas pageants?
There could be seminars, speakers and much social time.
"When did you portray the Christ child?"
"It was way back in 1955. I went for restrained and understated. From what I understand, my performance was well received."
"How did you deal with your Wise Men?"
"I sent them away with a subtle Don Corleone-like wave of my hand."