Lemme start by putting my cards on the table - I think it's morally wrong to be rich. In a world where people are starving to death for the want of a few dozen dollars a week, people with billion-dollar valuations and extravagances are among the worst people I can think of.
That said, I'm not going to stand here and say "if you don't give it all away, you're evil". It's absolutely a logarithmic thing, and even at $8m, there are a lot of questions and plans you have to make to ensure that you don't do the whole "sudden windfall" thing and end up worse off than before.
But I'm in a similar situation to you (sans windfall), and I know I'd feel awful not using at least some of that money to improve the lot of those less fortunate than myself. I keep a running list of organizations that I personally feel do plenty of good to causes that are important to me and don't just exist to funnel donations into operating expenses, just in case of a big exit or whatever, and I plan to start with 10% of the total and work my way up to as much as I can stand.
So definitely make sure you and your family are taken care of, take things slowly, try to get over the rush. But maybe re-watch Schindler's List, and consider investing as much as you can stand into good causes.