Gathering ideas for my new dojo :-)
Ivan Sanchez wrote about starting a coding dojo, and he rekons a Randori is best with 10 people or less. We will be more than 10 at JDojo@gbg. He suggests a prepared kata in that case. That might be possible. His favourite starting kata is KataMinesweeper.
Danilo Sato wrote about how to find suitable Katas, and suggests several for beginning dojos, including KataMinesweeper.
Gary Pollice wrote an article about what a coding dojo is, which is quite well explained, but doesn't give any specific advice for new dojos.
The guys running the finnish dojo have a similar article about what a coding dojo is, and some rules. They put a maximum of 15 participants on their randori. They also introduce "iterations" of 30 minutes, and spend 5 minutes planning in between.
Lots of ideas to think about, anway.