The Business Model Canvas is ideal for mapping a dynamically changing business model. If your social enterprise is established and stable then you may have other challenges, but for the new and developing enterprise BMC is a quick way of addressing the key issues in the model, stimulating conversation and formalising rapid evolution.
You should probably read Osterwalder and Pigneur's (2010) "Business model generation: a handbook for visionaries, game changers, and challengers." Also look at the host of videos and blogs about BMC. As long as your social enterprise is actually engaged in enterprise you will find it useful. If you want something specifically about BMC + Social Enterprise, I greatly enjoyed Ingrid Burkett's very accessible "Using the Business Model Canvas for Social Enterprise Design" https://mbs.edu/getmedia/91cc0d01-3641-4844-b34c-7aee15c8edaf/Business-Model-for-SE-Design-Burkett.pdf