After this, do a bit of research on goal programming or other approaches to multiobjective optimization. It could really help and depending on the approach, it's not that hard. It usually just adds a bunch of constraints or some precompuations to an already existing set of in/equalities for your model.
ALLOCATING CONFERENCE DELEGATES TO WORKSHOPS: A SPECIAL TIMETABLING PROBLEM --
"The problem of assigning delegates to workshops at a conference can be formulated as a timetabling problem. Such an assignment must take into account the preferences of the delegates, as well as the number of participants each workshop can accommodate. This paper will report on a heuristic solution technique for a special case of such a problem."