I went as a teenager with the youth group, some 12-14 years ago or thereabouts.
It was a really impressive event, and I’m glad I went. For the first time in my life, I felt like a part of something much bigger than myself. I saw thousands of other teens who cared about this stuff, too, and didn’t feel nearly so alone. As part of the trip, we went to the Basilica, something I can highly recommend anyone in the area do.
I’m not sure I’d go again; I think it is more geared towards youth anyhow, and it’s rather impractical with small kids if you don’t live in the area. However, if the kids want to go on a well-supervised trip once they’re old enough, I’d be happy to have them do so. Like I said, it was a really, really memorable experience.