There were a lot of children used in Vietnam. They would walk up to a helicopter and toss in a grenade, killing several U.S. soldiers in the process.
If these kids were truly innocent then this is an awful story and there is no justification. If this was a situation like Vietnam, though, then the parents' story that they were sending their kids out to collect dung doesn't pass the smell test.
is it reasonable to suggest a sort of age of self-determination wherein an individual becomes responsible for his own actions, whereas someone under that age is not guilty by proxy of their use by larger forces?
in other words, if a military force tells 8-year-old johnny that those guys in that helicopter are enemy invaders, and they're going to kill his mom if he doesn't toss a grenade in it, and he tosses the grenade and kills them, he is guilty of having done the deed, but it was no act of self-determination that inspired him; it was his position of ultimate helplessness within the context of his nation's struggle that forced him into it.