For breakfasts I used to work in a cafe where we would precook bacon on several trays and cool and drain the fat off and then store in the fridge and then crisp up when needed. It was actually very tasty and I use a similar method at home now although on a much smaller scale! I also always cook my sausages in the oven and could easily do at least 30 in one go.
For lunches I would be tempted to go down the soup route as you can make such large quantities easily. Something like a minestrone with loads of chunky veg or a chicken noodle soup would be my choices. Served with part baked baguettes and butter. I like to get a full baguette, spread with garlic butter and parsley and top with a mozzarella and cheddar blend then wrap in foil and put in the oven until all melty and delicious.
I agree a burger/hot dog night could be a good call! Very easy to cook a large amount of hotdogs, I did 40 recently without difficulty. I used the Dinos brand and served with various toppings including a chilli from the freezer and it went down a storm. There was a hot dog topping thread on here recently that could be useful if you go down that route. I'd also send someone to the chip shop for a few bags of chips to accompany them.
I would definitely do a few cottage pies/lasagnes in large foil trays and then serve with a variety of steamed veg or salads. Very easy to do large quantities of veg especially if you have a steamer.
Chilli is also one of my go tos for a crowd my chilli is famous among my family and is always requested. It is made with a combination of mince and diced beef and I serve it with rice, salsa, guacamole and tortilla chips and salad.
I love doing curries but would struggle to do enough for that many people as I like to do several different ones at a time and to get the quantities for everyone to have some would be a struggle. I think if I was going to I'd probably do shop bought bhaji, samosa, poppadoms , kachumber salad, chutneys, naan etc and then maybe a keema aloo, a chicken korma and some kind of vegetable curry .