My wife and I had a similar experience with the 1st England AMICA
Convention.  They refused to allow us to register our son because
"he wasn't considered a member."  Somehow they chose not to classify
children as part of a family membership.  It didn't matter that he'd
been to at least one or possibly two conventions prior to that, most
of the Chicago people knew him and there weren't lots of kids at the
other conventions but a few.

We weren't happy with the decision but accepted it.  As for AMICA
membership I'm still a Chicago Chapter member as well as a Texas
Chapter member now.

George Wilder