Never be too busy to laugh. Research says it, common sense knows it, and too often we forget the healing power of laughter. No crisis is too big to take time for a laugh. Tell them all you know. Keeping secrets is a bad way to build a team.
Shared knowledge builds loyalty and trust.
Being friendly doesn't mean going bar hopping or inviting them for Thanksgiving dinner. It means treating the volunteers in a friendly and respectful manner. Volunteers serving on a committee don't need to be close personal friends with the chairperson to do a good job. Invest your efforts in loyalty. Everyone, staff and volunteers alike will note your behavior.