Given the desire for anonymity, perhaps introductions between law students, families, and activists could occur at one-time events, or "parties".
Parties are very efficient vehicles for connection. It doesn't take long to meet everyone in a room. At these support parties, Participants could wear nametags that define their connection to a detainee or offer a service, with titles like "lawyer" or "activist". This could give families a place to connect with each other, as well as a place to look for help. After introductions are made, contact information could be exchanged, and subsequent meetings between specific people could provide a platform for collaboration and relationship building.
Participants could host these events at their homes to keep it private and anonymous. Events could occur at different times in different locations to create location-based nodes of community.