What were you expecting it to go to ?  I donate money realizing that it will be best used by whatever is needed the most, no strings attached. 
Maybe the family's largest pressing issue is what and how this happened. 
How do you know that the two parents are the ones who hired the lawyer and investigator? 
It sounded to me more like the grandmother was wanting to get a second opinion because she doesn't want blame put on her granddaughter or her daughter. 
No amount of money can bring back those beautiful children or buy peace of mind for the family. But what a second opinion or even third opinion can do is put to rest what actually caused the fire and put the responsibility where it needs to be if indeed there is another cause, which is certainly more plausible considering the wiring issues. Maybe as a result of this terrible tragedy the slumlords around your city will start to think about what their legal liabilities are when it comes to collecting money for substandard housing.