This is always fun to dream about :).
Step 1: Keep it QUIET, wait until check cleared before doing anything else (I would be in denial that this was really happening until I actually saw the numbers). Hire lawyer, hire accountant.
Step 2: Follow any advice of lawyer and accountant to protect assets and minimize taxes (may involve donation to charity...I'd much prefer a hefty donation to a good cause than a donation to Uncle Sam!). Possibly hire security depending on how successful I was at keeping it quiet (I don't know if winners can claim anonymously here). At this point I'd probably give a month's notice at work
Step 3: Work out my notice, quit my job.
Step 4: "Keep it quiet" is not going to work if I suddenly start buying everything under the sun. Keeping that in mind, I'd buy a modest house in the MCOL area I want to buy in now but can't afford (400k will get a nice, updated four bedroom in a good area with a yard and little work to do, perfect). And because it's been her dream since I was a little kid and my parents have done a ton for me, I'd also buy my mom a two bedroom oceanfront condo with a small trust set up to pay the property taxes, regime and HOA fees, with strict instructions to tell no one it came from me (they're well off enough that it's believable they bought it themselves). So we'll say 700k there (400k for the condo, 300k for the trust to pay 12k annually). I'm pretty sure I could stay in the guest room whenever I wanted so it's partially for me too ;).
Step 5: No other property purchases planned but I'd probably get a nicer car than the 14 year old Honda I drive now. Let's say 40k here.
Step 6: Lifestyle changes: Definitely would eat out a lot more, but I still love to cook and don't want to get fat eating out all the time. There would be some ridiculously extravagant shopping at Whole Foods (let's say 1000 a month, which is more than 3x what I spend now). Hire a maid a few times a week. I don't think I'd really need a gardener for a nice but not huge backyard, but maybe I'd hire a kid from the neighborhood to mow the lawn every now and then. Hire a personal trainer 3x a week to make sure I stay in shape. Umm...not sure how much all that would cost. Maybe 4k a month more than I spend now? I'd take some nice vacations too (two super extravagant weeks at Disney a year, two weeks in a new place, a week at the beach condo), so let's put 10k a year on vacations, for now (see Step 7).
Step 7: Travel. This is different than going on vacation every now and then. The reason this isn't in Step 7 is because I have an older kitty cat and can't leave him for months on end. Even with a kitty sitter coming in to take care of him I don't think that'd be enough. He's a rescue who grew up feral and took years to socialize, but now he's very social and adores his people, he would get lonely if I was gone for months at a time. Can't take him with me, he hates leaving the house and would be terrified. So this would probably have to wait for a few years until after kitty. This is fine, fancy vacations would be plenty for awhile and I'm a homebody, but I would like the slow travel experience of spending six months of the year traveling the world, home for the other six. Because this experience would be delayed for a few years, it would also give the stache time to compound. First class flights and nice hotels the entire way, I'll be too old for hostels at this point. Let's say 70k for six months of fancy slow travel.
So let's say of the 100 million I took home 40 million (hopefully much of that went to charity rather than Uncle Sam). I'll knock 1.5 million off for my house, mom's condo, new car (though I think that's an overestimate). 4% of 38.5 million means I can spend more than 1.5 million a year. Um, no, that is way too much. I'd keep 150k a year for my living expenses and I doubt I'd come close to spending all that. The rest (let's say 1 million a year to be safe) would go to charity. I'd focus on low income housing and public transportation, both of which are desperately needed in my area and largely ignored by the powers that be.
If Mr. Stachey and I got married (looking more and more likely), we'd have an amazing blow out wedding and honeymoon but not much else would change. He would obviously benefit from my win and I'd be happy to share, but there would be a prenup (we've actually had that 'what if' conversation before so this wouldn't be a surprise to him, he'd expect nothing less from me ;)).
If we had kids, again not much else would change provided they were healthy (150k is more than enough for a family), but I would buy them ONE modest car once they learned to drive (no repeats if they crash it and I don't pay speeding tickets), pay for their college and graduate school OR start up money for a business if they choose that path and have a plausible plan. I'd also buy their first (MODEST, no mansions) home for them so they could have one heck of a start in life. I think it'd be hypocritical to demand that my children work their butts off if I won the lottery and early retired at 30, but I want them to get through school, learn a skill that makes money and hopefully that they have a passion for.
BUT. This is all assuming my hypothetical children didn't grow up to be spoiled little shits who sit around and watch TV all day, do nothing for themselves or others or start getting into trouble. If that's the case, they get nothing but a swift boot out the door.
It's fun to dream :)