I was junged on this exact thing myself,
I left 4 kids in car to pop into post office, IMHO it is more dangerous to drag out 4 kids, 7,5,3 and 1 across a buzy main road than leave them in the car for literaly a minute or two.
I do however leave a baby monitor in the car and am able to listen to what they are up to when away from the car,
I was judged by someone as a "bad mother" she did not say this to me directly, she did not know I was in line of sight of the car at all times and that I had the baby monitor,
I truly believe that my children are SAFER in the situation I create than if I draged them across a main road, every day a child is either killed or seriously injured on our roads, dozens more are hurt,
Like others have said I think we need to realise what is really a danger and also walk a mile in someone else's shoes before we judge.