All of the boys teams went last year - this year only the 91's and '92's went. The older teams went to the college showcase at CESA.
The teams play in their appropriate age groups, much like any team of mixed ages (oldest player determines age of team).
The boys haven't had the opportunity to host teams from another country as the girls have (Germany) - so I guess it just depends on what the administators decide to pursue with each group.