some crazy woman decided that it would be a great idea to run up to us in the middle of the parade and plop her 5-6 year old child on my mare's back
WOW!!! That is insane! And if something bad were to happen she probably would have sued you ...
Some people really don't think sometimes!!
I would also get your mare used to having things thrown at her. During the parades here people throw candy and it gets a little crazy. I have had foam footballs thrown at me also.
The worst is the water guns that people spray horses with. I have been lucky enough that my horses didn't overreact to that but its not a good thing either.
As long as you are in a group though you should be fine, I hope you have fun!!!