One thing I have seen work to get people to build up confidence, healthier interactions etc is to break up large groups into groups of 5 and give them a reading

One thing I have seen work to get people to build up confidence, healthier interactions etc is to break up large groups into groups of 5 and give them a reading list, where one person every week is appointed to talk about a paper on the list. So 15 minutes present thoughts on the paper, 15 mins open for questions, doubts etc, 15 mins to go around the room where everyone talks about something they have learnt over the past week or some issue they have run into. The small group setting makes a big diff. I have seen lot of introverts feeling comfortable enough to open up and grow confident dealing with groups.