I'm not a big poker person, but given the amount of poker-related spam I've been getting lately, there must be a lot of people who are. If your attendees are among them, this might be of interest to you: World Poker Tour Launches 'Events' Division. According to PokerNews, World Poker Tour's events division will focus on providing poker events for companies, non-profits, and just about anyone else who would like to ante up.
They also hired Linda Spitz, the former senior vice president for Clear Channel, and Kim Ellis, who owns the meeting and event company, KKE Meetings & Events. But this is just one player in what appears to be a growing field. My colleague, Dave Kovaleski, wrote up U.S. Poker Series last spring, and I'm sure there are plenty more out there.
And if your folks are more into bridge, I remember doing a writeup a few years back about the American Contact Bridge League, which would be delighted to set up a tournament for your attendees, according to then-CEO Jay Baum.