That is a great story, and an amazingly lucky guy.
First, I'd pay of my debts (mortgage, etc), and help my kids pay for school and get started. I'm a big believer in self-sufficiency, so I would do it in a way that encouraged them to work hard, such as matching investments or giving gifts to help them get started in a career (help them move to a new location, first few months rent, etc).
Second, I would consider retiring, or working reduced hours in either my current job or a job that I found more preferential. I would travel and purchase some "things" that I have wanted (car, bicycles, whatever, nothing extravagant).
I would potentially use some of it to help good friends out or to treat them to something, like a big paid-for trip or something.
I would donate some to charity, but I would be very selective in what charities I chose.
Finally, I would leave a significant amount (with interest due to smart investing) to my kids. It is not unlikely that I would set it up in such a way that they inherited even more than I had (given 20-40 years to compound interest).