What should be the structure of this group?

I asked this question before, but I wasn't clear enough and I think people misunderstood what I was trying to ask. I'll rephrase my question. I am thinking of volunteering at a homeless shelter and starting a martial arts group. This "group" would not be a formal cl. There will be no belt system(obviously because they can't afford it). I might give out certificates if some people come regularly and learn certain self defense techniques. The group will be weekly and will consist of practical self defense techniques. I am a black belt in WTF Taekwondo. I will only teach what I know. There will be no hierarchy, no belts, etc. It will be just a group that supports each other in doing something constructive. What do you think? How should I go about this?