Hi Lisa!
Thanks for your question and for visiting the Disney Parks Moms Panel!
You bring up two of my absolute FAVORITE things about
Walt Disney World in the fall...
Mickey's Not-So-Scary Halloween Party at
Magic Kingdom and the Ride of the Headless Horseman. It is simply "Spooktacular" the way he kicks off the Mickey's Boo To You Parade by riding the length of the parade route. It really sets the mood. Unfortunately, once his ride is complete, he mysteriously disappears for the rest of the evening and nobody quite knows where he goes.
One suggestion I have...the Headless Horseman used to gallop the whole route but now seems to do more of a slow trot. This should enable you to at least capture him going by, or if you have a friend or family member with you, they could capture you with the Headless Horseman in the background if you time it right. I have done just that and it came out pretty decent.
That said, there are loads of other wonderful, and usually rare, character encounters that are available during the party.
I hope this helps and I wish you a magical trip!!
Chris