You should certainly apply. As I’ve said before, apply and then concentrate on other schools, because most kids don’t get in, unfortunately. I hope you do.
I would try to get the best documentation you can of your volunteer work. It sounds to me (and I’m at a distance) like the work with the autistic kid will make a better impression on admissions than the work as a sound technician.
You can address this in an essay, but that is you talking about you (Saddam Hussein could write in his college essay that he was a viewed as a kind and nurturing leader). Documented evidence is better than an essay. A newspaper article or even a write up in the church bulletin would help, and letters from the priest/pastor, someone involved in the church and the parents of the child could help. The more specifics these letters mention, the better. Think of how you can best make this stand out, and make yourself stand out form the other applicants.