It might depend on your level. I know of at least two Burbank CMs (yes, they're CM's, too) that are allowed to bring one guest each. (And I'm sure there are plenty more.)
I think it might also have to do with how many deductions you take on your W-4. I can't see some CM with a wife and three kids deciding whom to take each year.
It's basically if you are single you get to bring one guest, otherwise it's your immediate household.
In the late '80s and early '90s I used to attend the CM Party regularly. Don't know how they have evolved but back then they would have giant wrapped boxes placed along the fence in front of the entrance where everyone would deposit a "Toys For Tots" gift before they went through the tunnels.
They were always very calm and quiet evenings with several character photo setups scattered around the park. A CM would take your pic with a polaroid and put the print in a holiday folder for you. The crowds always were sparse but very friendly and quiet. And at that time the suits and other executives and administrative people would be acting as CMs.
At the exit they would pass out a tree ornament commemorating that year's party.
It always seemed to be colder than usual so we always wore very warm clothing. I think the lack of crowds and body heat contributed to that.
It's a fun evening and I hope you have a good time.
My daughter started working at DLR this last summer and has really enjoyed working there (She works in the Parade Tech group). She just got her invitation to the cast member holiday nights and was told she could invite a guest. Since her father is such a disneyphile she decided to invite me. Does anybody know what goes on at these parties? Sounds like fun.
When I worked at the park, I always took the mumster with me as my guest. I don't think a year has passed since, that she doesn't fondly remember the Holiday CM party. It really is a wonderful time. Don't miss out.