Short people versus tall ones... moving something under someone's feet can have a profoundly different effect on unsteady, clumbsy people versus those who are not that way.
Short people's butts hit the ground quicker, maybe not harming them as much. Move a section of underfoot floor just 3 inches sideways and a tall person might fall down hard and quick. Coordination is never a "given" factor with any body type or age of the person.
If someone is standing still and the floor moves slightly, maybe nothing happens. If the floor happens to move under the foot that is almost touching the ground as they step or walk a serious fall could maybe happen?
Lay a roller skate at a 90 degree angle to your foor, then step on it. Now imagine doing that and you don't realize the skate is there waiting for you.
Other moving things in a haunted house only have move just ever so slightly and the customer's reaction will be ten times extreme as compared to that same person at home, relaxed. OF course the dark and strangeness surrounding also adds to this factor.
Design and build anticipating the stupidest, unluckiest person coming through as a customer... then hope and pray they don't.
Keep the staggering, screaming drunks OUT and your life will be much less complicated.