Vent How do you get the point across?

I love going on field trip with DS's preschool class, but I hate it too. It just makes me cringe seeing some of the seats the parents bring in. I understand with the kids all being 4 and over that pretty much all parents bring in boosters since they're so much lighter to lug around. Unfortunately, most are nbb, but that's another vent I could go off about.

Here's the part that really bugged me...
There are 2 families that put their preschoolers in nbb in the front seats of their vans. Both have twins that take the captain chairs, but the back row is empty. So one of the dads drove today. The child was put in the back because another adult was riding with them (so obviously they had an extra space). After we got back to the school and started loading our own kids back in our cars I heard him tell his son to move his seat back to the front. WHY??? So I happened to glance over after he put the belt on... it was just about over his face because it was so high up!

I REALLY wanted to say something to the dad, but I don't know him at all. The thing is, last week I made up a handout that the teachers gave to all the parents talking about carseat safety and some facts and figures. We thought a subtle hint might help. Obviously it meant nothing to them. grrr...

What does every else do so these little things don't drive you crazy?

If you see an opening to educate, you do, but mostly you just say a little prayer and move on. That's all you can consistently do.