I don't want to go into great detail, but the fact of September 11, 2001 should still move Americans today. So, even though my students are currently living in a post-9/11 world, they need to know about an important piece of our recent history.
This video from Nick News is moving, informational, and kid-friendly. I've shown it to my students every year since it's airing on the 10 year anniversary.
Here's the link.