I was going to mention bin bags too!
Have you decided the full menu?
Are you allocating any elements to DH, DCs or DGuests?
Go through the entire menu with a pen and paper, list EVERYTHING needed for each part. Then go through it again and knock off things that appear more than once (so butter for bread, basting turkey, glazed carrots, mash and brandy butter only need mentioning once).
Check your cupboards - do you have any items as "standard"? (Probably lots but some people only need gravy powder at Christmas, for example). So you possibly have lots of things like salt and pepper, olive oil, dried herbs, gravy powder, flour, butter, etc. If you have enough for all your hosting plans (and taking into account other uses before then), knock it off the list.
Then re-do the list in the kind of order that the online shop has it.
Use that to check your online trollies and to make sure you have everything ordered.
Do you have candles, napkins, crackers, etc?
MAtches for candles and the fire? (And firewood or whatever you use?)
Any batteries needed? For toys, radios, hearing aids, clocks, ....and in what different sizes?
Items for breakfast.
Some things to nibble on - whether a fruit bowl left out, or crisps, dips, party platters etc?
Soft drinks, mixers, drinks for DCs, milk for coffee, etc.
Tea bags, coffee, ....anyone particularly like hot chocolate or Horlicks going to bed who isn't normally there?
Gaviscon is excellent idea.
Do you want to do any Christmas baking, mince pies, yule log, cookies or whatever? Do you need anything for that?
Are all your cooking trays and serving dishes still there from last year, and will last year's arrangements still work? Have you broken any cups or wineglasses that need replacing?
Make sure that, in the next couple of weeks, you get rid of as much rubbish and clutter ahead of time - wrap presents now and get rid of packaging, get rid of charity shop bags to the charity shops, empty out all the bins (bedrooms, study or other little used bins), and get all the big bins emptied in their cycles so that they have plenty of space. (We only have our bin emptied every 2 weeks, recycling and compost bins 1 week, the black waste bin the other week, and I am putting them all out in the next fortnight even though the waste and compost would probably wait another cycle or 2 in "normal" time).
And definitely hide a small bottle of a favourite tipple, a favourite chocolate or treat, and some bubble bath/bath bomb/luxury shower gel in your own Christmas Eve box for a few minutes time out.
(Do you have extra bleach. cleaning stuff, fairy liquid, dishwasher tablets etc?)