We were IN the elevator, before they closed the doors - and a kid was crying, the dad was making the kid go. THe CM asked the kid if they wanted to go and the Dad answered that the kid would be fine. THe CM said I am not asking YOU, and then asked the kid again- the kid said no and the CM offered the dad to stay on or not and meet the kid at the end. I think the Dad was embarassed, as well as mad, and got off with the child.
So, long story short you can exit after seeing the theming.
On a side note, my dd (whom wanted to ride) started crying just after the other kid left and the doors closed. Luckily we had been talking with the lady next to dd the whole line and we both helped to comfort her. The lady also knew that I had in no way forced her to try it.