If they offered a 'cancel' button, the kid can also hit the 'cancel' button on his way out and destroy all the other floor choices people already picked. I've

If they offered a 'cancel' button, the kid can also hit the 'cancel' button on his way out and destroy all the other floor choices people already picked. I've seen elevators where if you quickly press a button couple of times, the button will turn off (if it were already on). This of course doesn't protect you from the mischievous kid who presses every button possible.