Saw a mom with her little girl who is probably no more than 4 years old. They are seated together in the handicapped seat. The mom whispered something to the little girl and the girl got up instantly and asked a senior citizen to take their seats. It was very sweet. The little girl then made sure she was out of the doorway whenever someone walked in or out, and even when seats became open, she always pointed to anyone who looked "older" and asked her mom if she could ask them to sit down.
It was very cute and refreshing. Especially since there are so many 20 and 30 somethings who DO NOT get up for anyone!