I'd echo the thought to keep them moving and camping at a different location each night in a back country location. First, if you are away from a nearby parking lot it and they know they are deep in the woods they will be less inclined to wonder. The fact that they are experiencing moving scenery will help with boredom. They will probably hate it the first day but by the second day they will start to find the rhythm of walking. Third is that they get to practice setting up their tent and camp each night.
Make them (groups of 2) start their own fires using a firesteel (after teaching them how to do it). To make it easier you can use PJCB as the tinder. A small piece of hack saw blade can serve as scraper. Give each group a folding Sierra type saw to work with for wood prep. Don't let them cut live trees and the Sierra saw will limit what wood they try to attack. Make them cook their own pasta e.g. raman noodles or something on their own fire while you prep the complementary parts like the cut veggies and meat.
Joe's idea of the critter hunt is good, bird watching is also good if you know your birds. A demonstration of how to build an emergency shelter using materials in your kit like a space blanket etc. Demonstration of a first aid kit and how to use each item and multiple uses for different items.