If you needed a seat why on earth didn't you ask for one?
You expected the children to notice you, judge that you needed to sit down more than them, judge that no one else standing required the seat more than you, and offer it to you instead of the other nine standing adults.
You haven't said at any point you expected any of the adults to offer seats to you, or offer you their child's seats, only that the children were rude for not knowing to automatically offer you a seat.
I have a neurological illness and am sometimes overcome with exhaustion and have to sit down ,no choice. I have to ask for a seat as expecting other people to know how ill I am just from looking at me is unreasonable.
If I can't get a seat, I must sit on the floor, no matter how difficult or painful it is, because I cannot stand.
It sounds as though you are capable of standing for an hour, you just think someone else should have done so instead.