I could do the island thing as long as I could be sure my sisters & the pets were taken care of while I was gone.
For the money, I see a problem: How do you keep this a secret from the IRS? And how can you keep the spending secret when the stuff you buy is going to become obvious?
But assuming those 2 problems are resolved, I would pay off my house, buy an old Victorian house in a neighborhood more in keeping with my interests, and have it remodeled and furnished to my tastes (sticking to the vintage theme though). I would probably spend the bulk of the money on investments that would guarantee me an income so I could quit my job. Anything not spend on me would be spent on certain charities and on my sisters.
She will always carry on, something is lost, but something is found; they will keep on speaking her name, some things change, some stay the same