Making great teams
Group size is an important consideration. If resources and class size allow, the optimal number of group members for this activity would be 3-5. This will ensure all students are able to actively contribute while avoiding any ‘free-riding’.
For easy-to-follow tips about group selection and initiating collaborative challenges see this useful guide from the University of Sydney
Dynamic Approach
You may also consider a more dynamic approach in which either you or the students devise different roles based on the particular tasks involved in the challenge.
This approach will require your students to create a task list that answers these questions:
What are the different phases of your project?
To complete each phase, what steps will you need to take?
What roles or responsibilities will be necessary in completing these steps?
Who would be well suited to each of these roles?
How will you ensure that each group member will contribute equally with no ‘free riders’?
Create a task list.
Good resources
Washington University - Using Roles in Group Work
Vanderbilt University’s guide to formal and informal cooperative group structure
Illinois State’s collaborative learning guide with great discussion prompts https://education.illinoisstate.edu/downloads/casei/collaborative_learning_guidea.pdf
James Fester’s blog post about organization for problem based learning tasks
https://www.bie.org/blog/roles_in_pbl_three_approaches_for_organizing_group_tasks