I have done in the past, veggie soup, carrot and corridaner, or carrot and leek.
( made in advance) home made bread rolls.
veggie lasange with salad , peas or in winter roast potatos ( I do wack in a lot of calories)
double choc ripple cheesecake.
I make lasange in advance and freeze it.
the soup night before/and cheesecake, bread rolls in morning.
This was a lot of work in the end, but feeding 20 is!!
This christmas I am cooking christmas dinner for 17. am not looking forward to it.