Do you have an older, more seasoned camper who would be more suited to Lincoln's training needs? Or perhaps an assistant counselor? It sounds like he may be a bit much for "green riders" to handle, but, as you said, he has potential. I don't know what your logistical system is or how many campers you have, but maybe you could school him with your campers and their mounts, and let this year be an orientation for him into life as a camp horse. If you need a completely reliable, bombproof, kid safe, out the door camp horse, I would say keep looking. I don't know how active your horses need to be, but in my area there are a lot of older (20+) horses available, the tough thing is to find a well broke horse without one hoof in the grave and the other three on banana peels. Good luck in your search and with the campers!
A stubborn horse walks behind you, an impatient one in front of you, but a noble companion walks beside you ~ Unknown