Have your son in law hit a non-perimeter weighted club and see how much he likes those toe hits. He'll not only have buzzing hands, but a score that is even higher.
PS - Lengthen his irons an inch or so, go to a slightly lighter club (maybe), or have him step a bit closer to the ball. It sounds like he has a consistent miss, so there is a solution for him. (Mind you, if the toe strike is coming from an over the top move, the light iron will probably hurt, not help.)