If you want an honest answer, I'd have to say that I'd keep it.
I have no interest in going out and buying Lamborghinis or a big house, but it would be nice to have the security of $5 million. Who knows when it might come in handy? I could also have a little bit of fun with it. Maybe pick out a struggling family and help them out with a $50,000 donation.
I spend most of my time in the wilderness, so I wouldn't burn through the money. I might spend $500 on supplies each year, but that's about it.