Grief Counseling Session @ Work?

My company recently suffered a fatality on the job. As a result, we're arranging grief counseling for the crew involved. I'm not sure if my boss should attend. On the one hand, he'll definitely benefit from the session (he's taken it hard) also, he'd be leading by example (we're in construction, these guys aren't the pour-your-heart-out type). On the other hand, there's a concern that employees wont benefit fully from the session if their boss is around--they might hold back on expressing how they really feel. Any HR professionals or people with similar experiences that can offer advice? Do you think the benefits of his attending are outweighed by the detriment it might cause?