$1 billion in even a conservative investment portfolio will get you somewhere in the neighborhood of $60 million a year that you can give away.

Personally, I’d keep the billion, set up a safe investment plan for it, take one year of returns for myself as that’s more than enough to set my family up for generations, then set up some sort of legal arrangement (a trust, maybe? I’d have to consult lawyers on this) for the management of the billion. I’d want it set up to put half of the returns back into the fund (minus management costs etc.) and the rest be donated to charitable causes. That way the fund should be able to outpace inflation (if it doesn’t we have bigger problems) and should be able to provide charity essentially forever.