Should I feel bad because I'm not going to try to help the bus driver's crying children?
I'm not sure. Is there some reason that you aren't going to help them?
I'm busy with my own kids. I don't have time.
If you feel like you are too busy with your own children to take care of someone elses, then I find that reasonable.
They are still crying.
It's unfortunate that they're crying, but you have your own kids to take care of. The bus driver can't reasonably expect that someone else will care for their children.