Ok as a parent of many children who have played many sports through the years I am going to jump in. Both my sons have played baseball and soccer at pretty high travel levels, the equal of allstars at worlds. In order to step on the field the ref/umpire was handed a ring of picture ID's by the coach, each child had to step forward as their name was called and their face was matched with their picture. For regional and national playoffs the coach also had to carry a book that contained an OFFICIAL, meaning with the raised state seal, copy of everyone's birth certificate. Not a big deal you got it back at the end of play offs and the coaches were very careful with them. If an opposing coach questioned the age of a child the coach could pull out the real birth certificate and proof was immediate. The purpose of this really long winded explanation is why can't this be done at Worlds? Check picture ID's of athletes as they come into warmups or when they check in, which ever, and if there is a complaint, pull out the official birth certificate. If your gym is above board no big deal. But until this is policed there are always going to be complaints and concerns, founded and unfounded.