First off: What a horrific, tragic event. To lose a child, especially one so young, has got to be incredibly traumatic and my heart goes out to all involved. That said:
I think the first problem is less the dogs and more the parents not noticing when their child got out of the house.
That can happen, I don't really lay the fault on that too much.
How a family, with over half-a-dozen dogs, can lose track of a 21-month-old toddler is beyond me. Asking a 12-year-old to be responsible? In that environment? Sorry, no matter what breed of dog, no matter its reputation (and, perhaps even because
of its reputation), the responsibility falls on the adults of the household. They are, by definition, at fault