Let me start by saying that I've always hated recruitment fairs — you're treated like cattle and rarely get to speak to companies (read: HR departments) properly. I found it to be a similar situation with the milkroundabout event only instead of HR departments it was founders and developers.
I don't agree with "selling the brand" of milkroundabout as it will easily be confused with similarly named events/sites/companies. Instead aim to do guest lectures at universities on topics that are bound to get students interested.
If you're the ones with interesting work, why aren't you talking about what you do? Students already get told that they are under prepared for what working life is like and you can expose them to what you've done. You could easily compare this to what life was like at <insert safe boring company> before. If you're so inclined.
Pick topics that are interesting to the students that you want to attract. Then go on a tangent about start-ups, the culture, and the experience. If you show students what it's like to be in a start-up, they'll get involved and tell their friends.
In summary, sell them a better lifestyle than the usual suspects.