If someone is not prepared then we all have to stay in. I would be telling parents at pickup that you require their outdoor items daily (no matter what!). You decide when to go out or stay in and the kids need to be prepared either way. I have bins here for extra items to be left. I had one with no mitts today and luckily they had spares here in their bin.

We go out everyday unless it is -20 (temp or windchill- whichever is colder).