I do not know what airline your son flew on but anytime I have flown with my children or grandchildren the kids have always been treated like royalty. But they did behave.
I think it was Continental. My grandchild behaved pretty well for having to sit on dad’s lap all that distance. She was an angel anyway, you know. ALL granddaughters are JUST perfect! He’s 6’6 so it couldn’t have been too comfortable for him either.