On the eve of our wedding (also New Year's Eve) we had 25 people in our 800 square foot house! The one big advantage we had, being in FL, was that we could use unheated space. There was one party going on in the living room, and one party on the porch. But the bar was set up in the garage- guess where everybody was? If you're in a cold climate, you can keep food outside (protected from animals). I would designate one small room (if you can spare one) for coats and presents. Nothing fancy- just pile stuff up. Overnighters are always fun in a small house- we've had people sleeping in the living room, porch, you name it. Folks simply have to be flexible- let people know ahead of time what they are in for. We have some relatives that prefer a hotel rather than all that 'togetherness'. Our friends and family have always been understanding and accepting- we had a lot of fun times in that little house!

This really isn't a suggestion....but your situation reminded me of the time I was invited to visit a "pueblo". My friend's family home was 2 bedrooms and relatives had expanded to 30 people of all ages. They had every holiday together in this little house. I can't remember anything about the furniture, where the coats went, presents piled or how they cooked and served. The only thing remembered was everyone together, helping in the tiny kitchen, playing with children and all eating at one table in the kitchen. I don't think anyone even thought of needing room.

Now that I wrote this, am wondering why I have such angst over room in my kitchen for a table. The table above may well have been wood boards with a cloth on it....but certainly wasn't something even thought about. Memories can sure tell us what is really important in the scheme of life.

I'd try to keep everything as simple as possible. Try to plan a meal that doesn't require a lot of prep, so you don't have people who help bumping into each other while they're chopping and stirring (I like to do as much ahead of time as possible). Don't go overboard on decorating...IMO, a lot of visual clutter makes a small space look smaller. Designate an area for gifts. Maybe get a free standing rack for coats and put it in the basement, if necessary. As stated above, let people who don't already know that your house is small, but add that you're glad to have them. You don't say how long your guests will be staying or if you only have one bathroom. Those are factors that will also matter.
Good luck and let us know how it goes.

When I had my family stay with us one Christmas in our 900 sq ft apartment, I did a few things that helped preserve my sanity:

* Decide in advance where each guest would sleep, so there was no jockeying for position

* Buy a gigantic ham, which I forced the guests to eat in various guises during their stay

* Ask guests to be as "efficient" as possible in our one bathroom (shower only every other day, use one bath towel the whole time)

We had a long row of hooks near our back door, so we kept all the coats there (with shoes lined up on the floor below).

As for decor, I think we had a few tinsel garlands over the LR windows, a small Xmas tree, and that was pretty much it.

People are generally very flexible when they're visiting, particularly if they know the situation in advance. Most guests are more concerned with not being a burden than with creature comforts.

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On a humorous note, my grandmother used to determine in advance how much toilet paper each guest could use, and then inform them of their "allotment" at the beginning of their stay.