Of the seven people, the only people who were young enough to have been "the kid" at Elliston Barn, and still old enough to have been friends with Orvalle Tanner (Dumar/Sheriff Hardy's Dad) are : 

1. Sheriff Mcallister
2. Gale Bertram

Of these two, Sheriff Mcallister as Red John makes more sense. He and Tanner could've both been in Elliston Barn, and he's the one who could've most likely gotten Dumar a job in the Sheriff's office