One thing you really can't do is tell parents how they should and shouldn't raise their kids. They're just not going to hear it, unless they specifically ask for advice — and even then it's not a sure thing.
Everybody has a different way of doing it, and generally speaking, as long as no harm is coming to the kids, no way is really more wrong or right than the others. But what constitutes harm to the kids is more debatable than you might expect for some folks.