If an off site location is not in your budget then plan on having the party after office hours. For office Christmas parties usually employees will come back to the office and this way the people that would prefer to not be there do not have to deal with the party during office hours. If you would like to extend an invitation for the office Christmas party to everyone then that would probably be the most courteous thing to do just as long as you understand that not everyone is going to want to show.
For office Christmas parties it can be difficult to make everyone feel a part of the celebration. One of the more effective ways to make everyone feel a part of the party is to hold raffles for door prizes. Everyone is given a number, or series of numbers, when they enter and then the numbers are put into a bowl. As each prize comes up someone chooses a winner at random. That way the guy from the mailroom has just as much of a chance of winning as the VP of sales and nothing works better for office Christmas parties than watching the kid from the mailroom walk out of the party with the best door prize on the table. Make sure you don’t highlight any one particular person for the office Christmas party. It isn’t a retirement party and it isn’t a promotion party for an executive. It is the company Christmas party for the entire office to enjoy so it is best to just keep the individual congratulations for another time. You may also want to avoid making the Christmas party in memory of a departed colleague. There is a time and a place for a memorial and the company Christmas party is not that time or that place.
If you keep the office Christmas party to a general celebration with devices built in to include everyone then everyone will have a much better time. For office Christmas parties there is no time for reflection or personal recognition. It is a time for the whole office to get together and enjoy the holiday season. Make sure you also offer a taxi service if you are serving alcohol as that is the responsible thing to do.