Having a group assignment is DEFINITELY more work for the teacher than managing students who are participating individually only.
Pick group work very intentionally. EX: Will they need to work in teams on this sort of thing after this course is over? Are there teamwork related learning objectives in the course? Will diversity benefit the final outcome? Are there conflict/team management learning objectives in the course? Are there very few pieces of specialized equipment to go around? Etc...
Once you do assign a group effort, you suddently become not only the teacher of the class, but also the team manager for each group! Unlike a team manager, you don't get to interview and screen applicants for your teams. You must work with everyone you have, which means that on top of being an excellent and very organized manager, you must also be a compassionate leader. It takes more time to be compassionate, not less, so your communication must be efficient. By this I mean you must be a very good listener (both to what is being said, and also to what is being felt). I would advise one-on-one conversations with every student in addition to team-meetings with you and each team.
You must be vigilant. I have found myself doing spot checks of the un-engaged looking students, so they know that I will be assessing whether or not they know their stuff.
Like I said - more work not less, so prepare and assign group efforts wisely!
