Sarah,
Just a thought:
You might like to contact with the people working at
Disneyland
about what to expect when you are there for the Halloween
event. The more you know about what to expect, in terns of
how scary something is, the better you'll be prepared for teh trip.
I don't know if showing a video would help too much. It's a big
difference between what you see on a video and what you see
live.
The best advice is:
You know your child best. If you know your child gets easily frightened
it's probably best to avoid anything that would frighten your child.
Perhaps you could observe your child's play. And you might consider
playing dress up, too. Every chid is different.
You mighr even benefit from reading from this page;
http://pbskids.org/rogers/parentsteachers/theme/
There are some topics that deal with pretending, so you can read more
about Fred Rogers' thoughts about play and pretending there. That might also give you some ideas on how best to prepare your child for a trip to another place, too. This program was a good one for many children in the USA, too.
Good luck!