The two old grandmas were one of the many victims of the Los Angeles Earthquake. They were played by Betty Phillips and Georgina Hegedos.
The earthquake of Los Angeles
They are first seen slowly driving as Jackson was honking at them to get out of the way. Apparently, they were not aware of the situation as one of them calmly said to hold onto the eggs. They were shortly after presumably killed when a chunk of the ground suddenly burst up and crashes into it. Even if they did survive the crash they would have presumably died when the entire city of Los Angeles sinks underwater.