Ken,
I totally agree with Josie and Jim. There is NO way to fix an out-of-class assignment. Most groups WILL divide up the work because it is so difficult to meet that the only way to get it done is for individuals to either take turns or do parts. The bad thing is that the set of conditions created by out-of-class assignments ALWAYS reduces learning AND results in free-riders.
The other problem with the current assignment is that it is a case where "more is less" and doesn't meet any of the 4-S criteria. Even if you brought it into class so that students would be aware that they were working on the same problem and you could do a simultaneous report so that it fit 2 or the S's, it still wouldn't work for two reasons. One is that I don't think a task that general (pick 6 or 8 topics out of several chapters...--it is NOT a specific choice) would be seen by students as being significant. I'd bet that if you had students rate the assignment on a scale of 1 (busy-work) to 10 (significant) most would rate it 2 or lower. Also, assuming that each of the groups actually did a great job and created a "gallery walk", it would take several posters per team to represent their work. The net effect is that the walls of the classroom would be completely covered and it would take so long for students to figure out what issues needed to be discussed that there wouldn't be time to discuss them. That's why it's so important to require students to make a specific choice. For example, you might give them a specific business situate (e.g. a current news report of company with a specific problem) and have students choose THE topic that most likely got the company into trouble in the first place and/or the topic that the company CEO would benefit most from knowing about. Asking for a specific choice would both create the thinking and discussion within the teams and create a lively discussion after a simultaneous report.
I hope this helps.
Larry