Just about to retire so would do that at the expected point in a few months time, giving me time to plan for all the rest of the money!
Would give money to dc (obviously), but wouldn't tell them the extent of what I'd won, I think they'd be overwhelmed by it.
I have 2 friends who have long-term health issues. One has stopped work and is living very frugally on their savings, other is having to contiue working but really struggles and it doesn't seem sustainable. I'd give them both big sums (c£0.5m), but I'd want to do it anonymously. I even researched how this would be possible legally! Oh yes, I've dreamt of this lottery win for a while... 
There are 2 projects locally that I'd support - one is a community arts centre which needs to raise £20m, the other is a charity day centre for the elderly which limps along for year to year. A big injection of cash would make such a difference to their ability to plan for the future. Again I'd be an anonymous benefactor.
There would be a big house renovation project, including making our home as energy efficient as possible, and a garden makeover. I think people underestimate how much these things cost so hopefully that would go under the radar with my neighbours.
A bit of money for fantastic holidays and enough set aside for ocassional luxuries.
With what's left I'd set up a charitable trust over seen by us and dc, and every month we'd take it in turns to choose an existing small charity or community group and make a one-off donation of x amount. I think that would make my dc feel better about accepting their own good fortune.