My dad let me take his 300zx out for my junior prom (1994) and nothing happened. I think you're on the right track, your son seems to respect you so I wouldn't worry about him putting your car in a situation where anything could happen.
My senior prom I took my Oldsmobile Delta 88 Cutlass Supreme Royal - I wanted the backseat room
At least in the Z you won't have to worry about that!