You're taking a small group of 6 on a 3 week overland trip One of your passengers knows the region well and is constantly dominating the group with his stories and recommendations on what the gro?

Why not use his/her knowledge? Sometime before you go to a new place, maybe after dinner, have this person give a brief "lecture" on the place you will be visiting. People might even ask a few questions. Sometimes its nice to know a few items to look for before you start exploring. This way the person's feelings won't get hurt and people can then speak up and say "You told us that before."