Cats actually CAN differentiate between human adults and children and approach them differently. My super-aggressive formerly feral tom, who's also the oldest cat in my household, will bite and scratch for play and doesn't hold back when attacking people he doesn't like. However, he will back off and play nice with my 2-yr-old son and even allow petting in places which would trigger an attack if done by adults. Conversely, my 8 weeks old princess will sit peacefully when an adult pets her but avoids my grabby son by skillfully keeping herself a literal arms length away.