Answer: picking an idea after brainstorming multiple topics with others.
Explanation: in the past, when dealing with group projects it's best to brainstorm with everyone about different topics and see if everyone can come to an agreement. If you all come to an agreement then allot tasks to each person. Set deadlines for your group so you're not waiting til the last minute to do something or one person ends up doing all the work. Also by brainstorming it might become evident on who is more science oriented, which will help because they'll think in a unique way.
Hope this helps.