Not only would that ruin the expierience for the other riders, but you wouldn't capture the essence of the show. If you turn on your light it will light up things that can't normally be seen or even ruin an effect for the camera.
I tried a setting on my camera for low light situations. This worked the best. Also, if your camera has the feature, turn it to manual focus. The auto focus takes too much time trying to find what is the subject when you move throughout the ride making it blurry. One more thing, you will notice that when you watch your video later that there will be so much noise. This is because your camera picks up everything. Our ears can focus in on one thing but the camera will pick up other people's voices, machine noises, wheels, and overlapping soundtracks.
My Haunted Mansion video was hard to hear because the Host voice is coming from behind your head and the microphone was in front of me picking up all sorts of noises.
Rave º0º