While on the surface, this may seem like a good idea, until you consider some facts; 1) everyone was a child once, 2) parents represent more of the populace than single adults, 3) there are certain laws that explicitly prohibit discrimination, and most specify that one may not exclude another based on AGE.
I am someone who used to have the 'You kids get off my lawn' attitude before I became a parent, but I never - NEVER - supported excluding children from lawful activities, such as those being restricted based on age in this Yahoo piece. Movie theatres, supermarkets, airlines are all on the list. My local theatre had an 'adults only' showing of 'Cars 2' that was on more screens at more times than the 'kid-friendly' shows.
What a bunch of whiny, self-centered, spoiled BRATS we've raised! No, I don't mean the kids excluded from the fun, I mean the ADULTS that won't share.