First things first...
1. Set up annuities for my mother and my girlfriend's mother that ensure that they're comfortable for the rest of their lives...the idea is that they get the annuity income, but the principle remains in my name, so everyone's happy.

2. Set up college trust funds for both my children and my girlfriend's children to ensure that they have all expenses and a reasonable income during college, but also make it so that they can get the money when they've finished college and held a job for 8 years. In other words, they have to decide if they want to live a little lavishly during college and have less money later or if they want to have more money later...and yes, I'd still be the trust fund director with significant oversight even during college...oh, I'd do this for my nieces and nephews, too, so add four more!
3. Purchase my home for now; purchase my sister's home; purchase two neighbor's homes...figure out how to grant these houses to them without tax ramifications for them. Oh, and purchase a home for my mother, preferably far away from me!
4. Donate US$10,000,000 to
Heifer International
5. Donate US$10,000,000 to
The Salvation Army with a stipulation that it goes to social services and disaster relief and not to the church operations.
6. Donate US$10,000,000 to
Habitat for Humanity.
7. Get everything updated and fixed in my own home, purchase reasonable furnishings and such...but likely still from Ikea and not lavish because honestly? Having nice things is good, but I'm not all about having ridiculous excess.
8. Purchase
Volvo V50 T5 and maybe a
Miata
9. Hire an excellent tutor for my kids so that if we decide to travel, we can without impacting their schoolwork...but if they are studying the Roman Empire or the Chang Dynasty , why the heck NOT visit?
10. Look for a homestead of around 10 acres that is build-able and farm-able...
11. Oh, and since it's about to summer, I'd plan a crazy trip wherever we want to go...I'd love to show my kids PRC, Japan, Singapore, India, and Europe...take them where I've been...find new places to visit...here is where I will be lavish to an extent...I will have us travel business class and stay in reasonable hotels...
Ok, first week or three accomplished...
Next steps will depend on a number of things...finding additional charities that meet my criteria and interests, for example...