The shed! A basement is enclosed so you know nothing is going to jump out at you from most sides but during a trek outside at night...almost anything could "getcha!"
Again, safety is a concern but could you light the path with tiki torches? I paint them black and give them a little rust colored paint to make them look a little less tropical and a little more creepy. Right now they're really cheap too. You HAVE to keep people away from them but they do give off a lot of light...even from a good distance away. I'll sometimes pile up branches to form a barrier between the people and the torches.
Just a thought...safety is concern #1 but I definitely vote for the spooky shed!!!!
Or line the path with jack-o-lanterns...or candles centered in paper bags full of dirt or sand...or glow sticks.
How easy is this? http://www.ehow.com/how_5593413_make-luminaries.html
...and pray it doesn't rain.
and please post some photos whatever you decide!