Actually, there's not. Unless they are an armed threat, it's completely illegal to shoot them 'for being bad guys'. Unless they were killed on accident or in the crossfire of another battle, shooting unarmed civilians will merit murder charges, under military law.
If they were innocent, there's every reason to suspect they weren't innocent or they wouldn't have been there.
Huh? It's a crime to be in your house? They may have known about the IED attack, and odds are they did, but that doesn't make them different from most other families that lives near a major roadway in Iraq. Terrorists will set up wherever they want to for an attack, and execute entire families that rat them out or otherwise resist them.
"Weren't" was the operative word. The phrase, "If they weren't innocent" means either armed or hostile with the immediate ability to kill, not just being in the condition of being a "bad guy."
They were told long before to leave, from what I understand.