My favorite Halloween/fall kids stories were (naturally old ones!):

Georgie:

Nicest. ghost. ever. Makes Casper appear like a whiny troublemaker.

Don't ask me why I think of fall and Halloween with this next story, but I do. The story isn't that great either but the art and the story combine to create a great mood:

Ghost Town Treasure

It has to be the older edition. The new one with different art is about as romantic as the editions of Andrew Lang's fairy books butchered in the late seventies with some 'contemporary art' in lieu of Ford's victorian era masterpieces which fit the text. For the same reason, I dislike sci-fi reprints with updated art on the covers. Give me the original which is appropriate for the time it was written and printed.

This one was always fun:

How to Care for Your Monster

Light, fun, fair for the younger set.

There are some others but I can't think of them offhand.

Have fun with the story-time MA. Kids will remember and they will look back fondly.

;-)