I have thought this through to a possibly unhealthy degree.
Firstly, I second the no publicity idea!
I would buy myself a home outright. Somewhere local. Due to mobility issues it would be a decent sized bungalow and it may need some work. There may be the option of building. though I've no experience of managing such a project.
Speaking of property, my parents' place is not the best, mobility wise, so I may insist on having them chloroformed* and move them to a suitable property.
I would then do some things for family and friends, before looking into charities.**
What to do fro which family and friends and whether to make any stipulations is something I find difficult, especially with one person who is not known for financial sense, or indeed having money, or observing the law, or staying clean and sober...
One thing I may do is "pay" myself X amount a month and leave the rest in savings, perhaps using some now and then if need be. It would be a comfortable amount to cover essentials, bills and luxuries.
It may well make a big difference if the amount was 1 million or 10, though it may not. I struggle to conceive if such amounts and the interest they would accrue once initial spending is done.
*This is a joke, based on the fact that they have made quite clear that they have no intention of moving again.
** I have not read the link on the tax implications of gifts.