If you are selling this as a drop off I would figure 5oz of meat and 4oz serving of each side per person then tell them that you have it priced that way and if they will have some big eaters they may want to order extra
Example 30 people - 5oz pork 4oz each two sides per person $6.95 if you have big eaters they may want to order for 40-45 people to make sure they have enough. This way if they run out it is not your fault.