The fridge is your best bet. I haven't had any problem with them turning brown if they're not cut, so long as they are used fairly quickly. I've even kept them up to a week and they've been OK. From now to Christmas Eve shouldn't be an issue. If they had a bruise to begin with, however (from rough handling, too agressive squeezing to test ripeness, etc.) the flesh will be brown around the bruise. But it would've been brown even without the refrigeration.

I regularly make a salad out of sliced avocados and very thinly sliced sweet onions (Vidalias, Mauis, even red onions) layered together, and then seasoned with S&P and drizzled very lightly with good olive oil and red wine vinegar, You can add some sliced tomato too, if you got one at this time of year that's tasty. Very good combo of flavors.

Avocado also pairs well with grapefruit. And nothing, but nothing is better than a lovely seafood salad or cocktail of either tiny, sweet shrimp or good crabmeat, piled into the hole in the avocado where the seed was. A half an avocado per person is plenty, because its so rich. That seems to be to be a wonderfully decadent treat for Christmas Eve.

Avocados actually freeze pretty well, especially if you're planning to mash or puree them when you use them (I don't love the texture of frozen avocados if they're just sliced - they get a little too mushy). I discovered this when I was making baby food for my eldest daughter, and ever since I've tossed very ripe avocado halves into the freezer, in tightly sealed bags, if I'm not quite ready to use them when ripe.

The problem with refrigerating already ripe avocados is that the flesh quickly turns brown. I would not expect these avocados to be particularly attractive on Friday. At least, that is the case with the CA avocados I have bought in recent years. ;o)

This is called summer salad but it is so good - if you can still find plums:

http://www.food52.com/recipes/6130_plum_avocado_summer_salad

Also if you are worried about them keeping you can make salsa now and keep that for a couple days - I make this a lot, people go crazy for it!

http://www.food52.com/recipes/6436_salsa_asada

The salad of sliced grapefruit and avacados tossed with Helen Corbitt's poppyseed dressing is one of my favorites!

If by really ripe, you mean they are a good level of ripe to eat now, I think you'll be fine storing them in the fridge until Christmas Eve to use. I buy a bigger bag of avocades from Costco pretty often, and put them in the fridge once they ripen on the counter - they've been fine up to about a week and a half after I put them in the fridge.

Putting them in the fridge will slow down the ripening but it may not get you to Christmas Eve if they are already very ripe. My favorite avocado recipe involves tossing cubed avocado with diced red onion, diced roma tomato, cilantro, jalapeno, lime juice, salt, pepper, cumin, and lots of fresh crab meat. It is a crowd pleaser.