We've had to sort out both sides of parents homes/wills etc after they died and also 3 of the 4 with long term health conditions. An absolute nightmare as, despite wills being made, there were no POAs and their homes were full of "stuff" and finances disorganised. After we've been through that, we're not inflicting it on our DS!
Written wills and update every 5 years or so
Got POAs for both finances and health
Started to de-clutter the house and weed paperwork etc., half way through loft sorting into 3 piles of "keep", "tip" or "charity shop", doing the same with cupboards, shelves etc in the house as we go along. Not keeping anything without particular sentimental or financial value so cheap/naff ornaments are going. Sold loads of rarely used things like "best" cutlery and crockery, gravy boats, serving dishes etc, "posh" tablecloths and napkins etc. that we basically only use once a year - can do without! Same with clothes, weeded out our wardrobes down to things we actually wear which meant about 3/4 of what we used to have has been donated.
Consolidating bank accounts, pensions and investments to make it easier to sort out afterwards
Keep a list/file of exactly what finances we have, latest utility/broadband/sky bills, latest car and house insurance policy documents, so that either of us or our DS can quickly see what's what.
File of house stuff, i.e. deeds, purchase details (solicitor completion statement, copy of estate agent brochure), warranties/guarantees etc for home improvements, new windows, new boiler, etc. - everything else ditched (such as minor tradesmen bills, low value fixtures & fixtures bills etc).
File for each car with "log book", insurance, full service history garage bills, etc, to make it easier to sell when the time comes.
Drafted inheritance tax returns for us both to "prove" no IHT due, to make it easier for DS to go through probate. Will update every five years or so with updated wills to reflect changes in asset values etc.