Lusi

I will tell you what my mom does...

for 50 ppl she makes 2 big trays of pulao with almost 7-8 cups rice in each tray. My mom use whole leg pieces cut into 3-4 pieces. I think she normally use 20-25 whole leg pieces (cut into 3-4) in one tray.

Are you making both qorma and karahi? I would say make 1 of them. Don't make it too dry or too runny.
For salan, she again use whole leg pieces, get them cut from your butcher in 3-4 pieces depending on the size of the leg. Again I think she normally gets somewhere like 25-30 whole legs cut in 3-4 pieces.

If you want two curry dishes, make a non meat salan with korma like mix vegetable or aloo bhujiya or bengan or chana salan or something like that.

For sweet dish you can use buckets of ice cream, cake, and fruit dish like cantaloupe (spell) or water melon.

Oh and also have pita or some naan like 20 cut in half.

Have salad + rita and you are good to go.