I think there is a mod to install a fifth seat in the small cargo area, provided such and such weights are not exceeded. Should have to dig into my old manuals though.
Also, the news indicate that "The children were between the ages of 10 and 14 years old", their weight plus the light fuel load for the short scenic flight shouldn't make of CG a big deal on the accident. Of course, we should wait for the final report to see what really happened.
I read it was usual for the owner of the small air taxi to reward local students each year. What a sad sad story!
There are no stupid questions... just stupid people!