Teaching: Groups of Three

With my first set of courses done, I'm looking ahead to the next set. One course in particular offers an interesting challenge.

The course is basically a set of game design exercises, meant for small groups (three or four; I think five would be excessive). Each exercise would go something like this:
Tuesday in class: We play a game or set of games, and analyze them from a game design perspective. The choice of games is relevant to what we'll be doing for the project.
Tuesday-Thursday, homework: Students perform some kind of preliminary market analysis that will be relevant to the project, so they won't be starting from square one. For example, if they'll be designing a game to fit a license, this is where they'd take a look at the license.
Thursday in class: Project is assigned. Groups brainstorm ideas together, and submit their best idea at the end of class.
Thursday-Tuesday, homework: Groups take their best idea and flesh it out into a full concept (one or two pages). Something that would be presentable at a business meeting.

Now, the obvious problem here is that it's an awful lot of work outside of class.

Here's what I'd like to do: delegate the homeworks to one person in each group, and rotate it around. With groups of three students each, and nine projects total in the course, that means each student would have a total of six homeworks, none more than a page or two. Much more manageable.

But what do I do if the number of students isn't divisible by 3?