One of my friends passed along this tip and another friend picked it up with great success. Since there’s one front seat available, and more than one kid, no child can “call shotgun” or ask to sit there. They can, however, ask if a sibling may sit there. There’s no fighting about turns or who called it first or who got other privileges today. It won’ be right for everybody, but for some families, it’s a good solution.
I suspect that when/if I have kids, I might use this policy for quite a few privileges that can’t multiply to go around.