From what I observed (I saw this video on another forum a while back), they did everything they were supposed to.
It was just a simple mistake, and although it resulted in the death of many non-combatants... it was nobody's fault.
The Apache saw what appeared to be hostiles.
Groups of armed men, with no information on them being one of the allied tribes or any US/Allied soldiers, they opened fire.
When the van pulled up, they thought it was taking weapons and ****, so they opened fire once again.
It was sad the kids got hurt, but seriously it's not like they intended for it to happen.
And how could they have known they were there? Whomever edited this video had all the time in the world to pour over and zoom in and find the kids or proof they were civilians, but the Apache gunner didn't have that time.
He didn't have any real time to think or any indication they were friendlies.
And if you look at part of the video (not sure which part), you'll notice a guy was saying something like "Their fault, don't bring your kids to a battle" or something or other.
IMO, that simple statement is him showing how bad he felt, but still being ALL MANLY AND TOUGH AND A SOLDIER, he didn't want to act like a little ***** in front of his buddies, so he acted like it meant nothing.
But that's just my opinion on the matter.