Ok one thing I want to say about the trailer:
I wouldn't show the boogeyman.
Look at how much hype was made by the War of the Worlds trailer. It was forbidden to see what the alien tripods looked like or sounded like.
Look at how much hype is created by Super 8. Don't see the bad guy, but you hear it bashing out a god damn reinforced steel barricaded cell they've got whatever it is held in.
Anyway.. I'd make more of a mystery about the Boogeyman in the trailer so when people watch the movie it's a surprise or they are curious to what it looks like.