I would teach basic waltz steps. Start with a box, turning box and a corner step. Talk about body position and rise and fall. Social ballroom implies that people will be dancing in a social setting. The most important thing is floorcraft. If you teach a routine, people will rely on it and there will be no lead or follow. I have seen it many times, when the man deviates from the routine, the woman will stop dancing to declare, "that's not what comes next." As well, they will annoy others on the dance floor. Dancers who only know a routine start and stop, walk back to the corner and can dance with no one except their partner. This takes the 'social' out of social dancing.