I think the better seats should be given to the elderly, or as a privilege of the people who arrive early. I have no issue with someone saving a seat while his wife is taking the child to the restroom, so a family can sit together. Other than that, there should be a 5-10 minute limit on seat-holding. I cannot stand when someone holds a few seats for a friend who may not arrive, or worse, whispers back and forth.
As far as the rule that all adults should sit first, it is not easy to keep a child still if they are not sitting. (Perhaps not all children, I had 2 with special needs). I know there are different rules for different shuls, and not everyone is as considerate as CTLawyer when they are not going to be there. But really, consideration for others would solve most of these problems.
Just last week I was in a waiting room when an elderly couple walked in, and 1 seat remained. It bothered me tremendously that the teen girl and her mother that were already seated barely glanced up from their phone and magazine. I stood and could only hope that the girl noticed that people out there would be kind to a stranger, but I know it is rare today.