This is my tried and true go-to warm up activity for teaching EFL students about Halloween. I've found even when I'm teaching in international contexts, my students know something about Halloween from TV and movies.
This easy activity gives them some statements about Halloween and asks them to decide if they're true or false. So it draws on a lot of their background knowledge. Then follow it up by going over the answers and giving them some background information on the holiday.
Or turn it into a webquest. Get them to search for the answers OR the sources of the false statements (which mostly all apply to other holidays).
So it's a great discussion and culture lesson. I use it as my go-to warm up for Halloween, but it could also be a review or a part of a larger unit.
Follow it up with any Halloween lesson. Might I recommend:
Movie of Death, A Genre Approach to Reading and Writing a Scary Story