Just to clarify, privacy was never much of an issue. I guess I've always tried to get away from the trail to poop, just as a courtesy to other hikers. I'd like my son to do the same, but he doesn't really have the same kind of foresight that I do. Of course, part of this is outdoor teaching, so I'll have to keep working with him. And he's not a toddler; he'll be nine in August. Honestly, I think he's just so adapted to modern plumbing that his system assumes there will be a toilet nearby anytime he has to go. He does well to let us know in advance that he has to poop, but his idea of advanced notice is about 20 minutes. Not a lot of help. I'm pretty sure he can hold it if necessary, but I'm not really willing to take that chance. I was a child myself once.

I'm learning a lot, since he is our only child, about what to expect in worse case scenarios. For example, we took a tour of some beautiful caverns last year, with multiple reminders beforehand that there are NO bathrooms once inside the caverns. We tried to anticipate by drinking well before entering and relieving ourselves beforehand. Sure enough, at the lowest point in the tour our son had to pee, and he was desperate. I hadn't been in a situation before where just turning to pee could have significant influence on the surrounding environment. I forever thank the courteous fellow in our party with multiple kids who carried an empty water bottle just for those situations.

Anyway, to reiterate what others have said, I believe that if you gotta go, you gotta go. I'll think about the bags. I've never carried poop, and I only entertain the idea on a philosophical level. Thanks to everyone's input on this, and I welcome any more ideas.