It blows my mind how YOU'RE not understanding this. You know who set this up and are actually adults? The moms. They're responsible since they intentionally made this happen. Money aside, regardless of what "errands" they ran, they chose to put incapable minors in charge of a bunch of children. I don't disagree that OP may have had a responsibility to avoid a lapse in supervision to the children. The context of the situation bears a lot of weight. If you had parents who made decisions like this, do you think you'd have the knowledge and experience to make all the right choices when you were a teenager? It's hard to expect a teenager to be "the adult" when the adults aren't either.