Do your homework!  What kind of foods do they like, what can you make, what can you buy, does anyone have food allergies and what is your budget are some of the questions you need to ask yourself.  Draft up a menu and don't forget snacks, bread and drinks.  Pin that up or put it on the fridge for a few days.  You will probably add or subtract to it in that time.

Now you need a grocery list for each dish on your menu.  Check your recipes so you don't forget anything.  Work out when you are going to buy everything.  Perishables will have to be left until last but other goods can be bought ahead and stored.  Work out how you are going to make all the food and which ones you will buy in.  Don't forget the crock pot recipes here as they can be made a day or two before your dinner/lunch.

Make the dishes you can make and where possible set the table or tables beforehand.  You don't want any stress on the day.  Clean the house thoroughly days before and quickly clean/dust/mop only if needed on the day.  Allow plenty of time to get yourself ready and dressed.   We sometimes forget ourselves.  I have been caught many a time still doing my hair when guests have arrived.  Get someone to help you set up the food and serve when ready.

Enjoy your celebration and have a Merry Christmas and a Happy New Year.