I would obviously tell my immediate family with the condition that it not be shared with anyone who isn't blood, I know that seems harsh but money changes people. So without further ado, here's what I'd do.
1. Take care of my familys mortgages and bills so they have a clean slate.
2. Put money into trust funds for my nieces and nephews and of course my own kids.
3. Give lump sums to my parents, brothers and in-laws.
4. Have a solicitor draft anonymous cheques to my closest friends.
5. Give to childrens charities, hospitals and local schools.
6. Help the elderly, homeless and animal charities.
7. Buy some gold bars and then buy some more.
8. Get an English butler.
The possibilities are endless, but the main thing I would do is keep it low key, stay out of the limelight and try and do as much good with it as possible without any recognition.