This seems incredibly easy. I can easily just fin a knife and start hunting, maybe get a gun and I'm grand. That's not a lot of children.
I think the concern would come from when they start forming packs and hunting each other. I could confidently take out two or even three ten year olds, but five or six after they make spears would be concerning
the ten billion dollars honestly trivializes the entire thing. you could hire an army of mercenaries to systematically execute everyone who isn't you
I don't know, they don't sound brave enough. Maybe, though.
Just burn the land, Fence the area and wait about 2-3 weeks.
Their kids so they should not last to long.