I am in Australia too but as my parents are originally from Europe we do the whole roast lunch (usually pork)with all the trimmings (thank God for air conditioning lol), but we do tend to have fruit salad for dessert as the summer fruit is usually fantastic. We decorate with a tree and some lights (don't tend to go too crazy although there are plenty around here that do) We usually open our gifts on Christmas morning although when I was little we open some after midnight Mass. There are usually lots of different "carols by candlelight" events held which is usually great on a lovely summer's evening but this year they have all been rained out so far. There are 2 really big carols by candlelight events one in Sydney and one in Melbourne which are televised and the get some amazing talent to sing the carols.
Australia is such a multicultural country that there are so many different traditions, our neighbours are from Portugal and they have slightly different traditions, it's always fun to learn about them.
Merry Christmas to you all.