It is said that social media is word of mouth on a grand scale. Your neighbours will engage with your online presence far more often than in any other way. Take every opportunity to solicit and present every good thing said about your work. If you really want to make a difference in your community encourage members to blog and post about how their lives have been affected.
In the world of marketing, brands have discovered that if they tell their audience that they are the best, 14% of listeners will believe them. If you tell ten friends the very same thing about the brand, 90% of your friends will believe it. If your members encourage their neighbours to believe in the value your many volunteer hours create you’re pretty much assured of a growing membership.