My relations that live in New Zealand tell me that there are lots of people out camping or at their Baches (holiday homes) for Christmas.
Many towns have a Santa parade with decorated floats, bands and marching girls. This can be any time from mid November onwards and is really a commercial event but much enjoyed by all.
Many people have a Christmas Tree in their homes and decorate it like people in the USA or UK.
Many New Zealanders have a barbecue for Christmas lunch and this is becoming more popular. The food cooked on the barbecue is often ham slices or even venison or some other kind of exotic meat. Shrimps and other fish are also barbecued!
Desserts are also very popular! Many still have a hot fruit pudding with custard and ice cream but cold desserts are popular. These include pavlova and whipped cream, meringues, cold fruit salad, jelly and ice cream. Drinks will include a range of soft drinks. Those who like it often over do the alcoholic drinks too. Here's a recipe for pavlova.
My relations have an English type Christmas meal in the middle of June (New Zealand's mid winter)! This meal will often be hot food such as roast chicken, roast lamb, cold ham, hot roast vegetables such as potatoes, pumpkin, sweet potato, and other root vegetables and also greens such as peas. Coleslaw is increasing in popularity. All with gravy!
They open their presents on Christmas day once the whole family is all together. This is usually before the Christmas lunch.
In the Maori language Happy/Merry Christmas is 'Meri Kirihimete'. Happy/Merry Christmas in lots more languages.