You may not like my response, but I don't care for parades nor will I ever do another parade, too many things can go wrong and the general public is ignorant when it comes to horses and crowds in general.
Last year and the year before, our town has a big 4th of July parade. Both times, a team of draft horses were attacked by a big dog, one was a Pit Bull that someone let loose, biting the horses legs, belly and barking and snapping at them. The year after that the dog bit the horse in the nose, chest, and legs, the horses became dangerous and thank goodness the driver knew what to do and had a quick way to escape before it because a wreck. I have seen others throw fire works right in front of the horses, balloons flying and moving around, candy being thrown, etc...
I myself got talked into doing a neighboring towns "small" parade of mostly animals last December. We were asked to carry Santa and Mrs. Clause in our surrey and it was pulled by my most steady mare Smoke, who is a been there done that Percheron. When we got there, hitched up she seemed okay with the llama's, the pot belly pig in a tutu, all the sights and sounds. People in vehicles though, they cut me off, the sped by me, and while standing in line a dually truck came by me to get in front of me but couldn't so there I was, literally trapped, an ambulance behind me, the dually and flat bed next to me, and another vehicle and flat bed in front of me with screaming kids. Smoke did the parade, she pranced and danced the whole time, thank goodness I had 2 outwalkers with me. When we got back to the trailer I had a group move so I could go between two trailers, I turned Smoke then let her fast trot as the surrey isn't light and we were going up an incline. I was half way up, mind you she has brass bells on her harness, a lady walks out in front of me and when I yelled "MOVE" my husband grabbed her and jerked her out of my way. I would not of been able to stop Smoke on that incline without her sliding backwards from the weight or her jack knifing our carriage so I was fully prepared to run the woman over than risk my horse.
So, while you can prepare for a lot of things, personally, my horse and their health and well being are MORE important to me than some parade with screaming kids and people. Are horses expected in parades? Absolutely. My hat is off to those who can take their horse out and do that, but you cannot know what the crowd will do or control the people in it.
Good luck to you. Just my personal experience and .02 worth.