To reply to JustAHumanBean my interpretation of what happened at the end is that the POV switched to that of the invaders, just like it did when it switched to Laura after Charlie died. The monster that spits out people from its ears is a car (which three people get out of: Laura, Kenny and the Meteorologist) and the offering that they give to the intruders is chocolate. If you chose to give something back in return I think the intruders offer a meteorite. The round, dark thing is beyond me though.
Great story if a little short - definitely worth the read! (play?) :)