Disclaimer: I am not an educator and I don’t have children (though many friends think I’ve never really matured past 8 or so….).
If it’s outside and allowed, I’d start off the whole thing by showing them how to build a fire (by assisting them as they build a fire) and talk about how building a fire is one of the most basic and important skills to know for backpackers (not lecturing, but ‘chatting’ as they/you build the fire, and how smaller fires are much better than big fires, etc.).
Then I’d use the fire to assist them in making some cool backpacking treats. (They do most of the work, keeps them engaged).
Then we’d all sit around the campfire and I’d begin to tell them a cool backpacking story – like the time I walked 500 miles! Who wants to hear about the time I walked 500 miles in the mountains! (I think lots of hand would go up).
Then tell them a story about one of your long hikes. Doing this will help keep their attention (you’re telling a cool story, not ‘teaching’ them about backpacking), and allow you to touch on a lot of different aspects of backpacking. Allow questions during the story. Make up stuff if necessary to touch on areas on which you’d like to impart information.
ie: One night it rained so hard I thought I might float away in my tent!
Q: How did you keep your stuff dry?
A: allows you to talk about site selection, proper shelter for the conditions, etc.
ie: And then I came around a corner and there was a big bear in the middle of the trail!
Q: Were you scared?
A: Well, I was a little nervous, I can tell you that! But before I left on the trip I did some research about bears, and what I found out was… allows you to talk about bears and other animals and how to react to different situations. Also allows you to touch on proper planning as part of any trip.
etc. etc.
Storytelling is an effective way of imparting information, especially for younger audiences. They learn alot when they don’t think you’re actually teaching them anything, and have a tendency to stay better engaged if they don’t think they’re in a ‘learning’ situation, but instead just having fun.