> my style has been to explain that there's really no such thing as ghosts or monsters, they're just stories and toys

I think you're already doing it right.

> My wife's preference is to not even bother with theory, and just frame things in practical ways he understands: "The ghost lives in the shop with his ghost friends. It doesn't like sunlight and it's not going to come to our home."

The two of you need to get your stories straight - you need to agree an approach with each other. Just for you to flatly contradict one another is going to confuse him and potentially make things more scary.

It might help for you to talk it over with him in more detail. You might have to repeat the same message in different forms over a bunch of different occasions:

 - "Some people like to tell scary stories, but that doesn't mean they're real."

 - "If you don't like that kind of story, I won't tell you any of them. That's ok."

 - "That's just pretend. Those people are dressing up to play a game."

 - "We're not afraid of pretend XYZ's, are we? Let's practise telling them to go away: GO AWAY, SILLY POO-POO XYZ's!"

As in that last example, you can combine your approach (they're just fiction) with your wife's approach (within-story reasons why the scary things aren't a threat) by making up stories together with him - and emphasising that you're making up a story together and it's all just pretend and so on - and in the stories the ghosts are totally un-threatening: you and him together call them rude names (toilet humour is good here, because humour will make him less scared, and nothing is more humorous to a 3-year-old than bodily functions) and *they* run away scared of *you*. And then emphasising at the end that the whole thing is just a silly story and they don't exist and aren't real. That kind of approach can help him find the courage to not-be-scared even of things which he knows aren't real.

We've found these useful:<br>
 - ["Thomas & Friends" episode on Halloween][1] (book and TV episode both available),<br>
 - [Angelina's Halloween][2] (be warned - extremely charming illustrations).


> **Draw out his fears.**

> Encourage him to talk about the imaginary monster and ask him to draw a picture of what he thinks the monster looks like. This way you respect his feelings and convey that you empathize with him.

> **Don't chase the monster away.**

> An oft-advised fearbuster is for parent and child to walk into the bedroom, look under the bed and in the closet, and "chase the monster out of the bedroom." Not only is this downright dishonest, but all it does is reinforce to your child that there really is a monster in his bedroom—which might make matters worse.

> **Tell the truth.**

> Emphasize to your child that monsters are only pretend characters on TV or in storybooks. It's a parent's job to help her child separate real from imaginary characters.

http://www.parenting.com/article/ask-dr-sears-mashing-monster-fears

If trick-or-treaters are a problem, I'd just send him off to bed early so he doesn't see them. Or if they come round too early for that, sit with him (in a room upstairs or at the back of the house) for an extra buch of stories or a movie or some kind of positive-attention activity you can do together.


  [1]: http://ttte.wikia.com/wiki/Halloween
  [2]: http://www.amazon.com/dp/014240621X