I will be cutting back on cards too. I didn't receive cards from some relatives last year, so gives me an excuse to stop. Fortunately, DH can make use of his works internal post which goes to sites at different towns for some colleagues, and we deliver what we can by hand. Cards and crackers are very rarely bought at full price.
We put up the same tree and decorations, this will be our tree's 10th Christmas. Never saw the point of buying lots of new stuff in different colourways every year. I have a good browse around all the displays at shops and garden centres, and might possibly buy one thing! But only if I love it and the price is acceptable. I find that just looking is as satisfying as actually buying something, when I calculate how much I've saved by not doing so! I feel the same about new outfits to wear on Christmas day, unless it's a longed for gift from someone in which case it would be rude not to wear it. And new PJ's, dressing gowns and slippers, apparently all so that they will look nice in the photos according to my friend. But is that enough of a reason to justify overspending and running up debts I thought to myself, fine if you can afford it. There is absolutely nothing wrong with budgeting carefully and spending within your means.
Let GP's or aunties/uncles buy the DC advent calendars. I know tree chocs aren't essential, but you could wrap 5 choc buttons/dolly mixtures/mini jelly babies etc in twists of clingfilm and hang them on tree with a loop of thread, use to fill reusable advent calendars too, you could get quite big bags of sweets cheaply from Poundland, Aldi etc. They don't have to be Christmas sweets. You could also hang individual toffees on the tree (the ones in foil and coloured cellophane) with a thread loop attached, which look pretty and also bulk out very few decorations.
I plan menus for the Christmas period, mainly so that I don't have to puzzle my middle-aged brain about what to have, but also I can buy only what I need, and factor in use of leftovers. Keeps costs down because I don't waste it if there isn't excess to go off. We only have packets of ready shelled nuts here!t No relatives to go to or entertain at ours so just have a nice roast lunch at home.