I put the blame on the pilot, not the kids. How many times have your passengers asked to see your pilot's certificate? Not many people even know what one looks like.
My point is that the owner of the RV-10 represented himself as a pilot and the kids (reasonably) assumed that meant he was FAA certified and competent. This all goes out the window if the kids knew the pilot was drinking, but so far that is just a guess based on the time of day.
Before anyone starts calling for more regulations/"checks" etc.. remember these types of accidents are extremely rare. Flying at night, no pilot's certificate, overloaded on people and possibly booze... there are no common sense rules the FAA could implement to have stopped this guy.