How should I handle it when the small group discussion has more of a Sunday School - "Encouraging fellow Christians" feel than open discussion?

This is a very important question and one that needs to be dealt with quickly and sensitively. If this issue is not addressed it creates and environment that feels threatening and even confusing to the guest who know nothing about Christianity.

Here are a few ideas:

When you sense this happening, interject a question like, "This makes sense to people who would consider themselves to be Christians, but what would you say to someone who is not sure about Jesus?"
Or try this type of question, " Thanks for sharing your thoughts, but can you remember what this question was like for you before you were a Christian?"
Then at the end of the eve you may want to pull aside that person or people who were creating the "Sunday School" feel let them be aware that not everyone is a Christian and we really want the course to feel safe for them then appeal to them to see themselves as helping to create a safe environment for guests who are seekers.