You ask two really great questions. For the first, on whether you should use someone like you describe as a recommender, I would say a qualified 'yes,' since this person seems to have witnessed your leadership abilities and community impact. As long as they are willing to go into detail about these things in a recommendation, and as long as they have a genuine interest in you and your success in business school and beyond, I would think they could write a good recommendation, in fact, perhaps even one which stands out from the proverbial crowd. If, however, they have had very limited exposure to how you work and the impact you make, I might look for someone who knows you more deeply.
As for the family charity, of course you will get "credit" from the adcom for the work you have done on it, but just be sure not to use any family members as recommenders. To the extent you can demonstrate real impact instead of just being a figurehead it would make your application more legitimate. Hope this helps.