Set up a trust to invest the money, from the compounding returns, use a sustainable portion of the dividends to fund a cause you believe will help change the world. Be very explicit to the trust managers as to the long term instructions of the trust.
With compound market returns the million dollars could be worth $40 million in 50 years and would be distributing af a sustainable 3% dividend, 1.2 million a year to a cause you believe in.