You can have people dressed as "aliens" at Jupiter Point, like in the movie
Zombies/or aliens in the plane crash per normal
Going down or up the hill grass people, and inflatable guys along with people yelling look up and using a sound system to make it sound like the "alien" creature is above you
Near the bates motel have the Chimp that is covered in blood attacking a "dead" person on the ground and chase after those who look scared
Boom...done and its fun