Most restaurants that have party rooms have event planners just for this purpose. Take some of the suggestions here and call them and ask to speak to that person. They can help you plan a menu to fit your budget.
Most of them have a menu for events that is cheaper than the per person meals on their menu. We did my husband's graduation party at WNM on Deacon, and they did a buffet style meal with salad, wings, chicken tenders, tea and sides. I *think*, I've slept since then, we were able to bring our own sodas and keg.