Hi Ivy - not exactly a team-building exercise, but one thing we've tried is a "progressive dinner" where the directors sit at one table for the first course, and discuss a particular topic related to upcoming planning/decisions, etc., then change seats for the next course of the meal, so that the people at the table are different and the question is different.  It gives them a chance to discuss important topics in smaller groups where there is more opportunity for each person to contribute than there might be during a large meeting.