What to cook for 500 people?

Every week I do volunteering work that involves cooking almost 500 meals for homeless people. We gather at 6pm and start cooking and packing the food (often we also have fruit, salad, desert, as well as clothes, etc) and then from 9pm to 1am we drive around the city (I live in Lisbon, Portugal by the way) and give them away.

What we usually prepare is spaghetti with wheat meat and vegetables.

They love the food we cook but a few have asked us to cook something different for them.

So, my question to you is, what else can we cook for all these people?
Obviously something that is cheap and quickly done is the best option but I will evaluate all the answers!

Many thanks!