Hello! I'm portuguese and I thought I should tell you what chances that lawsuit woud have in Portugal: zero.
A car is a potentially dangerous machine. It moves. It is heavy. People must take appropriate care AND the responsability for their doings. It was the father's choice to buy the car, it was his choice not to buy the optional camera, it was his choice to use the car that day, it was his choice to reverse. I agree he must be a very distressed man right now, but he mut take the blame. Or the "business end of a shotgun", as you say. Trying to pass the blame to Nissan is not very honest.
What next? If I get a speeding ticket, can I sue Ford because my Focus can exceed the speed limit?