At my current job, we have three Christmas parties (yes, we are spoiled):
Party #1 - Includes everyone in the company, retired employees, and board members and everyone is welcome to bring a guest. It's in the evening on a Friday night (tomorrow night actually) at a banquet hall with open bar, live band, huge appetizer smorgasbord. It's perfectly fine with us for the +1 to be a friend or relative. It would be very weird for someone to bring a child to this event, fortunately it has not happened so far.
Party #2 - A very nice dinner at a high dollar restaurant for the employees in my department, again +1's are invited, and some of the single people have brought a friend or close relative. Again, that is perfectly normal and ok with us. This is also an adult event and no one has ever tried to bring a child.
Party #3 - This is held at the office on the day before our two day Christmas holiday. The foold is usually pot luck or deli trays, each department does their own thing but there's usually lots of mingling and visiting between departments. Now this is where it gets odd to me. You would think, actually being at our office, that it would be employees only. However, family members are invited and some do show up. I have never invited my DH, he's usually working anyway. Over the 10 years I've been here, it has become increasingly chaotic as some families have increased in size. Our department head for example, has gone from having 1 grandchild to 8 grandchildren (some are step-granchildren), and ALL of them come. All of these children, plus the other employees' children, just completely run amok in a fairly small area. There's not even enough seating for everyone. Did I say it was chaotic? It really is! I'm a quiet type of person and my nerves just can't take it for long. Maybe I'm just a Scrooge or a Grinch, but I no longer enjoy this event at all. I make a brief showing to be polite and get some food, then I return to my office, which is fortunately in a completely different area!