For some reason I can't comment. Anyone care to explain?
However, Tom, I think the speed-dating is an excellent idea. Putting everyone in the same awkward situation always seems to warm people to one another, it forces everyone to be a whole lot more open than they'd like. If we're going to do this then we should come up with a list of recommended conversation topics that we can leave at the entrance, one for each guest. On one side it could have the conversation topics and then on the other some kind of manifesto about us and why we're here. Make it a proper nice document, something for people to take home.