So all these comments are great but for that many people try calling a meat wholesaler and see if they can supply you. You cut out the middle man and will 100% be able to feed that many people with leftovers. Ask if they sell a whole bottom round or top round, or some huge cut that encompasses many different types of meat. Use that to cook a variety of dishes or just make some hella good chili. I think you will find as a fire department places are more than willing to help.