It would help to know how many square meters (or feet) of mat space do you have and what´s the maximum number of practitioners you would like to accommodate per session. I figured (and this is a totally unscientific approach) the minimum area for a confortable coupled practice (breakfalls and all) to be 9 square meters. Thus a regular area of say 36 square meters may confortably accommodate 8 adult practitioners (10 children) plus the instructor. Going back to your original question, for a recent seminar with Fujita sensei we managed to pack 120 practitioners in a 180 square meter area...we figured the best approach was to sit half of them, taking turns so everybody had equal practice time.
