These comments are wonderful.
 
I think multi-media and crossover works can be very powerful if done thoughtfully. They're not as effective if done for meta-reasons such as marketing. I completely agree with both of you that there are lots of assumptions made about audiences' need for sensory stimulation, and that efforts to cross-pollinate merely to lure new patrons--especially younger ones--can be patronizing and lack sincerity.
 
Although it's been a while since I was a college student, I remember the feeling of liberation well. It was the first time in my life that I was introduced to nuances of social dynamics in a sophisticated way (especially through sociology and women's studies classes), and I was always on the lookout for hidden paradigms that I could defy. Younger people approach life in a much more straightforward way, and they're beautifully unaware of the criticisms leveled towards classical music. They listen to it on its own terms. My guess is that parents, relatives, and friends who enjoy classical repertoire might involve young kids more often, but the implicit message that classical music isn't entertaining and that you therefore need to make it palatable (or provide childcare) is discouraging. And the concert setting itself is difficult for anyone--kids or adults--who have difficulty sitting for long periods of time.
 
The truth is, I'm younger than the average classical music patron and I would love to go to more concerts. But I would rather do it with my child because I love being with him, not just because I can't find a babysitter. The current economic situation doesn't make risk-taking easy, but downtown organizations cater to the after-work crowd with short concerts at earlier times. Why not do the same for families?

"If we wait until kids meet current standards of concert etiquette, it might be too late." I think that's a critical point. Like a language, the understanding and appreciation of classical music - on an intuitive level - is acquired much more easily by children than by adults.
To carry the "language" metaphor a step further: Pretty much all the music in the public sphere these days - in advertising, on most TV shows, in the background at your local supermarket - is in a pop/rock idiom. (I'm old enough to remember when this wasn't the case!) We're surrounded by it, so that children are raised on it by default. They are comfortable, or fluent, in this idiom. When adults with this background hear classical music, it will be at least somewhat foreign to them. Even if they enjoy it, they will still feel more at home back in "pop-world." Hence, while some of us go to hear The Messiah as a matter of course, bringing our friends along remains a tough sell.
What to do?
One answer has to be arts education; another the kid-friendly concerts (not just kids' concerts!) already mentioned on this blog. I would mention one other way to address this. One particularly discouraging aspect of "pop-world" is the constant presence of video. It comes as no surprise that video is being brought in at artistic events, not as an art form but just as a kind of attention-grabber and -keeper. Andrew Patner recently decried this phenomenon in his review of a couple of local dance performances; though I didn't attend the performances in question, it was easy to recall similar experiences. We don't seem to trust that audiences - and not just children! - will be able to remain engaged with the work unless we throw some video at them. It's a self-fulfilling prophecy, of course. Early exposure to classical music will enable the child to learn that "language." Perhaps just as important is early exposure to one thing at a time, whether it's music, reading, painting, dance, etc. Let's train our children to pay attention, and not to expect or even require a big fancy show!