There's always loads going on at Christmas, but doesn't usually get confirmed until the week or two before!
If it's a traditional dinner you're after then quite a few restaurants will do one, and you can reserved tables at selected restaurants by clicking the tab on the restaurants page.
As for parties, most bars will have something going on whether live music or a cheesy disco! Check back on Arinsal.co.uk closer to the time and see what's going on!