I will try to rely on natural light during the walkthrough haunt for all of the outdoor scenes where possible, aside from accent lights for emphasis and effect.  There is something about the shadowplay cause by ambient light that cannot be recreated with dragging out floodlights and spotlights.  Besides, what the eye can't fully see (regarding detail on the props and actors), the mind automatically fills in and interprets... usually not for the mental calm of the viewer.  My little friend pictured above is obviously no real threat in full sunlight or fully illuminated by lamp.  But in moonlight, I expect even he will get a few reactions.  The vines that are not seen here, but are nearby, have a tendency to reach out and try to grab you when you walk past them in the moonlight.  It would be a pity to lose that by flooding the area with electric lights.