The fireworks are different for the halloween party than normal wishes. They are indeed reallly cool.
One piece of advice I would give is to not go on a Saturday or weekend night and not on halloween itself or anything silly like that because the crowds will be insane.
Last halloween, we went to MNSSHP on a saturday in late september, and it was SOLD OUT. The park was so packed it was kind of unpleasant and defeated the purpose of going to get on the rides. We ended up riding only TTA, BTM, and HM that night.
On the other hand, the fireworks and the parade were awesome. The park was decorated pretty cool. I've never seen MK like that before. If you love HM, now is the time to do it because it has upped the spookiness factor for the night. The music is louder, the building is darker, and the CMs are more rigid. Loved it.
We did not trick or treat at all and I was the only one in costume, but you get the trick or treat bags when you come in anyway, and while waiting for the fireworks and parade, CMs do come around to fill your bags. We ended up with lots of chocolate candies. In fact, I didn't see any candy that wasn't chocolate, which is fine with me because I love chocolate.
In the end, we thought it was worth it because the fireworks and parade were spectacular and it was a unique experience. On the other hand, we probably wont' do it again because it was so crowded.
So if you are going to go on a weeknight, or if you enjoy watching people in costume, or are willing to pay for just the parade and fireworks, then go. I had a great time. Other members of my party, not so much.. it just depends.