As this is a christmas party when you give your Christmas speech expect your listeners to have had an alcoholic drink or two. This may make them a little less likely to want to stand (or sit) and listen for a long time. Also be aware of the fact that you might have been celebrating eith an alcohollic drink. If possible wait until after you have given your speech to indulge!
If you're aware of the fact that they will have been drinking for quite some time before you speak, try to shorten your speech a little and make it very informal.
Your Christmas speech might be looking forward to Christmas Day and the holiday ahead, it might be looking back at the year, it might be very religious and want to remind people of the religious reason for Christmas and the good will involved, it might be about the importance of family or it may be more commercial talking about presents and spending.
You may want to prepare a speech before hand and if so I would suggest you make a few headings on a piece of paper to remind you of what you want to say. If the speech is in a more formal setting I would suggest you write the whole speech out and possibly read it. People would rather listen to a well thought out speech that is easy to listen to and to understand being read from a sheet than the muddled ramblings of someone who thought they could speak 'off the cuff'. Speakers who appear to do this effortlessly are usually experienced speakers who know what they want to say from memory because they have said it so many times!
Make sure you leave plently of pauses between each new thought so that the listeners get a chance to take in what you've said. It's better to give a short christmas speech with adequate pauses than to give a longer speech full of more information but spoken so quickly that no one has a chance to understand it.
If you think you do speak too quickly or too quietly have a look here for tips and help on giving any speech. The most important things to remember are to open your mouth so that the sound can get out, pause at the end of a sentence and make eye contact with the listeners. If you are reading from notes don't be ashamed do them, don't try to hide them.
If your child has been chosen to perform in a school play this Christmas and you want to give them a bit of extra help have a look at this page where you will find lots of tips about practicing for a play.
If you have to read in church this Christmas and would like some tips specifically for reading in Church please read this page.