Eileen, Its sounds as though we have similar Sons as my son eats a very restricted diet too. His Christmas Meal is always: Brandied and Ginger Orange cut into segments for Starters, Then a Huge Multi layered Salad, with every thing I can pile up and some sort of hard cheese, though he does like croquest potatoes and will sometimes have a Yorkshire Pudding too.
I thought of Pate too, as I am a veggie and only yesterday I made myself a chestnut pate, for my Christmas Lunch, which is very nice, though includes so many other ingredients. There is also Lentil and Aubergine pate, but again ingredients might contain things he won't eat.
It is frustrating, but perhaps he would just prefer what you gave him last year, whatever that was. I know my Son doesn't like to deviate. It is amazing he is six foot as he doesn't eat for that height. Good Luck and I will keep scouring my Recipe Books for you, and get back if anything suitable catches my eye. :) busy_lizzie