We've done MNSSHP a few times now and it is a brilliant evening.
Get to MK early to avoid the crowds arriving for 7pm start (it's a ticket-only event so there is a maximum number of people allowed, usually around the 20,000 mark - although this seems a lot, it's not really when you compare to usual crowds in the park). You will be given a wristband to wear to show you are there for the party. You will then be told to go to a specific land (we had to go to tomorrowland last time, brilliant riding space moutain with no queues!).
You will be given a trick or treat bag which you WILL fill with goodies. All around the park are huge green inflatable "pumpkins" - these show where the CMs are dishing out their candy. There are usually characters in each area (apart from when the parades are on which are well worth watching - especially the beginning when the headless horseman starts it off).
One of the most popular attractions is (naturally

) Haunted Mansion and the Qs can be large for this, so if this is a deffo on your list to do, get over there first.
There are a number of photo sessions around the park - and yes, they're free and the prints arrive back home within about 10 - 14 days. Ask for one copy for each of your party, you each get one then. It has a nice border on it with the date, so a very nice keapsake.
As for dressing up - whatever you want to do. I would say 50% of people dress up, probably 30% really going to town, especially the little children. If you don't feel like dressing up, that's really not a problem. Some families and large groups don't wear fancy dress as such, but all have on the same t-shirt with logos or family names - they look really good.
Try WalMarts of KMart - fabulous costumes for around $15-20 for adults, $10 or so for kids, all depending one what you choose. There is loads of choice. Half the fun is looking at all the halloween stuff in the shops - bet you won't be able to NOT come home with some.
We have tended to eat before heading to MNSSP, around 4pm, then headed straight over to MK. But around 9.30 - 10pm we have to have our traditional Cosmic Ray's chicken sandwich - just wouldn't be the same without having one!
I am really going to miss not doing MNSSHP this year since we're going in August - have a wonderful time
