Have a horror-movie marathon with fun spooky-themed snacks.
Make lots of autumn crafts (e.g. embroider autumn leaves, make clay pumpkins, paper chains).
Dress up for Halloween.
Carve and/or paint pumpkins.
Go to a bonfire and watch the fireworks on Bonfire Night. Bring marshmallows and muffins to toast.
See the Northern Lights (??!).
Do an autumn-themed scavenger hunt in the woods.
Have a marathon viewing session of Gilmore Girls/Over the Garden Wall/any other cosy show.
Go to the Halloween lock-in at the castle dungeons.
Gothic Horror Night.