brunch cocktail + snack?

For a non-alcoholic drink, this sparkling tea is lovely: http://food52.com/recipes/13245_orange_green_tea_sparkler

This will sound boring - toasted mini bagels (including some gluten-free). But if you offer both plain and fancier toppings, there's a better chance everyone will eat something before "progressing" to the alcohol. Have a great soiree!

Love Miranda and Sam's ideas...my first thought was the Bloody Mary but after Sam's post (he had me at "Scotch egg")...I'd go with that and as an activity you could have a "Mini Olympic Event" since London is hosting the summer games. As horse people, we would suggest "stick pony show jumping". (use string mops from the dollar store) but you could pick your favorite event and award medals!

I'd normally be all over a bloody mary bar. But given it's a 'progressive' brunch...that going to be more than likely done--unless subby steps up first!

Are you familiar with "Pimms Cup" a spicy gin based liquor, that's very refreshing and surprisingly light.
It's normally served with a cucumber spear and soda water (or ginger ale).
Very english. To keep with the english theme, how about some cucumber or watercress sandwiches. Or Scotch eggs, cut into quarters. Scotch eggs are boiled peeled eggs, warped in ground sausage meat. (Jimmy Deans mild is just fine). Use a rolling pin to make little disks to wrap the eggs, roll in bread crumbs bake (or fry, I do bake). Cool, cut into quarters.

What about an elaborate bloody mary bar? You could look to the Prune bloody mary menu for inspiration as far as mix-ins and garnishes - hard boiled eggs, pickled radishes, pickled beets, green beans, cocktail shrimp, sardines, beef jerky, the list goes on and on! With enough garnish, it's basically a meal in itself! http://www.prunerestaurant.com/

My brother makes a wonderful cocktail with prosecco or champagne and juice -- blood orange, pear, and raspberry are three that I've had and they were all really good. You could maybe do a "buffet" of sorts. Or a mix and match. Also, when I was little, my grandmother used to give us "sunrises" for breakfast when we stayed over -- orange juice and cranberry juice mixed. I didn't realize until college that those were based on tequilla sunrises....she omitted the tequilla, obviously, but something like that would mean you'd have options in case there are abstainers in the group (although given the games and the "day of debauchery" it doesn't sound like there are!). Activity....is charades too lame? You could have a theme to the things that people need to act out or make up a bunch of cards in advance and have everyone choose from a bowl. Anyway, it sounds like a really fun day. Enjoy!

Lastnightsdinner, I love the deviled egg idea.

SKK, still thinking on what the activity should be, and open to ideas if anyone has any. Last year included twister, rooftop swing dancing, guitar serenading, and more.

I like to make these for brunch: http://food52.com/recipes/15238_salmon_and_avocado_toasts. I usually add the avocado at the last minute, but otherwise they are pretty easy to assemble a bit ahead of time.

As for a cocktail, this is my go-to: http://food52.com/recipes/14962_blood_orange_and_ginger_punch. If you want to dial down the booze at 11am, why not try it with Prosecco, Cava or Champagne instead of the vodka?

Wow, would love to live in your neighborhood! Given your house is before noon you may want to start with a lighter drink. http://food52.com/recipes/15034_allans_spritz_aperol is wonderful and easy to mix ahead. The ice cubes in the glasses are an important component!

For an appetizer my go to's are http://food52.com/recipes/8908_roasted_fennel_white_bean_dip and/or great sliced baguette with cheeses and fruits.

What is your activity by the way?

One of my favorite pairings is pretty classic: deviled eggs with an ice cold Martini. You can make the eggs ahead of time, of course, and the drinks are easy to batch up and serve from a pitcher - no shaking required. We used to serve them that way at cocktail parties, back when we had them :)