[BenLurkin]

Meeting for meals would be ideal, along with opportunities for some low key competitive and cooperative pursuits.

Chess would be my choice (if they ever decide to send a fat old guy into space), or cards, playing music, forming a small choir -- maybe they could vie for who has the best results in keeping in good physical condition.

[RightWhale]

Music would be good. All astronauts should have some interest in performance, and some experience in public performance. But, music is also competitive and can bring out some very bad social traits. Best keep the group sessions to once a week, not the same day as the weekly dinner.