I don't have kids yet, and remembering back to sixth grade is sometimes a stretch, but I think we could have handled that sort of trip without major problems. I do think the experience will be enhanced if you talk with your son about the experience, but that's true of most educational field trips.
Actually, I think it's the perfect age to go. They're old enough to some sense that history isn't all
Washington Crossing the Delaware and "Mr. Watson, come here, I need you." They're either headed for jr. high or already in middle school - which means that before too long the "cooler than you" fences will be too fortified to allow any impact. That doesn't mean it will be easy or fun, but learning that not everything is easy or fun in a controlled setting is a valuable lesson itself.
Oh, and when I was in sixth grade we did the whole "
Pioneer Farms" thing. What a snoozer that was. We had to do this whole unit in preparation of making pioneer toys and crafts and crap. We were way too old to be making wooden spoon dolls. It would have been great for 4th graders, maybe.