I think it seems normal to introduce yourself as what everyone usually calls you. You are more likely to respond to a nickname than your real name in most cases. Especially if it is for volunteer work. I have a friend that never goes by his first name, only his middle name, so he doesn't reply when you call him my his real first name. I think if you are volunteering and working with a group of people trying to accomplish something as a team, you need to be alert and know when someone needs you lol.