DO you have potatoes and vegetables?
Do you have loo roll and bin liners? Tin foil and cling film?
Do you have milk for tea/coffee?
Do you have breakfast items?
Do you need butter for stuffing?
Do you need stock cubes, Bisto gravy powder/granules, or full on ready-made gravy?
Do you have drinks, alcohol and non-alcohol, and mixers and soft drinks?
Do you have headache, upset stomach, cold/flu remedies, and tissues?
Do you need firelighters and matches?
Do you need cream or custard for desert?
Sorry, I know that's all a bit random, but hopefully it helps prompt you.
I'd start with dinner on Christmas Eve, breakfast on Christmas morning, the main meal, any snacks, and breakfast on Boxing Day - what do you have and what do you need for those, and go from there.