I have 6 wheels but 35 kids in class so our problem is about the same. I have a requirement of 1 week on the wheel by everyone and the rest of the kids are working on a variety of hand building projects. Since everyone spends the week on the wheel it works out pretty well at the end. You have to be a little flexible --some kids really worry about not starting the other projects on time so you can't be too quick to post grades.
I wouldn't use the quick center deal--let them learn how to do it!!