I agree with Cheshire Figment.
If you have not been before, the Trick or Treating might not be exactly what you are thinking. On the special
MNSSHP map, they have candy stations listed with a Goofy's Candy Company icon. When you go to that location, you will see a large marker with that icon that shows where to go. At most locations, there will be line of people moving pretty quickly toward the candy distribution spot. The candy is in very large tubs and the CMs handing it out just reach in grab a handful for each trick or treated. There is not a lot of time or light for them to be able to do anything special for any special needs.
We have gone every year for the past 5 or 6 years. We do collect the candy ( maybe that is a term that describes the process better than trick or treat), but there is a lot that our DD can't eat due to her disabilities ( no hard or sticky candies). We sort through the candy when we get back to our room, separate out some she can eat ( or DH and I want to eat). We bring the rest home with us and give it out along with other candy to trick or treaters who come to our house on Halloween.
There is a lot to see at MNSSHP and you may find that your child is not that interested after the first few candy collections. It seems like a long time for the party, but by the time you wait for and watch the parade and fireworks, you have spent a lot of time and need to prioritize what you want to do - candy vs characters.