Help! Catering for my wife's 50th Birthday?

We've got fifty guests coming to my house to help celebrate my wife's 50th Birthday next weekend. My wife hates nibble food. Seems lately every time we go out these days hosts are serving finger foods, tiny little tit bits of deliciously arranged things that people walk around your house with and slop all over the floor, hide in pot plants and under cushions and so on....

So I thought we'd have a good hardy meal.

I have a few large pots and a stove. I thought I could prepare a few days before, a 20 litre pot of devilled sausages, a 10 litre pot of mashed potatos and 5 litres of mushy peas, and then everyone can sit down and enjoy a delicious feast.

Do you think I have the quantities right?