I used to lead children's concerts in a town where the rudeness of the parents far exceeded that of the children. We finally invited the superintendent of schools to welcome everyone at the beginning of the concert, and to make firm, pointed reminders about concert etiquette, adding that anyone who failed to comply would be asked to leave, concluding that we all wanted to support and encourage our wonderful children in the arts as well as everywhere else. It worked wonders- too bad that man was driven out of town on a rail (for other reasons) by a short-sighted school committee.
Educate, communicate, and when necessary, spell out the expectations. This culture is so used to canned entertainment and the noisy crowds of the sports world that many of them really don't know what's expected!