Since there are only two groups on this canoe trip, you can remove only one of them from the trio. B and C are both reasonable choices. I've found that kids who cause trouble back home are often wonderful in the outdoors. The wilderness is foreign turf to most teenagers, and respect is earned by doing more than your fair share in camp and on the portages. If you want to really evaluate a piece of equipment, give it to a teenager for a week.
Kids have an uncanny way of damaging or losing whatever they touch.
On one of my trips a boy burned up a new boot and part of his sleeping bag. He also lost a wool shirt and life jacket. For this reason do not borrow canoes and gear from anyone whose friendship you want to retain. Renting is safer, especially if the kids know they will have to pay for damages. A twenty dollar damage deposit, to be reimbursed at trip's end, will make the point abundantly clear.