The Coromandel is an absolute mecca for mountain biking. And the Yuletide is a great time to indulge in some leisurely touring of the area, sampling the best rides while dedicating heaps of time to eating, drinking, swimming, reading and other essential activities as defined by Maslow.
Bust out of Wellington and head north (if you're from out of town then add a couple days to sample the city's great tracks or boogie back for the Mountain Bike Festival in March). Hit the emergency stop button at Paraparaumu and cholesterol load on a Kapiti ice cream. Further on, stretch the legs at Tree Trunk Gorge - a great track just off the Desert Road. It takes about 2 - 3 hours, has blow-me-away scenery and seems like it's downhill for the entire loop. If you've got time then put the Tongariro Forest Crossing on your list as well. It's handy to have a couple of cars though to shuttle between the start and finish of the track.
Taupo. Check out Rainbow Lodge Backpackers for accommodation. Nowhere else can you get as many Far Side cartoons in the toilet for such a reasonable price (but there's often a queue for the loo). There's tons of biking. If you're feeling up to a longish day head out to the western side of the Lake and explore the Pureora Forest Park. Closer to town are the Craters of the Moon. This playground of single track is usually bone dry and a hoot for screaming down dips and slaloming through trees. After a couple of hours of adrenalin at the Craters, head to the Spa Park (a couple of klicks up Spa Road on the left) for a soak in the hot stream. You'll find them at the start of the Aratiatia walkway - look for the steam rising where the stream flows into the Waikato. Mmmm.
Rotorua is on the way to Coromandel and it's sacrilege not to stop and play in the Whakarewarewa Forest. Score a map of the forest from the Forestry Corp Visitors Centre in the Redwood Grove and go wild. Afterwards chow down at the excellent Fat Dog Café opposite the Court house on Arawa Street.
Whangamata is a good base for riding and beaching around the Coromandel. Unfortunately over Christmas the place swells to the size of Auckland (mainly because most of Auckland seems to be there) and accommodation can be tricky. Avoid the usual free camping spots - you're likely to be served with a trespass notice at some anti-social hour. This of course didn't happen to us, so the following year we wised up and rented a little house. We squeezed heaps of us in to reduce the cost (around $20 a week) and eventually recovered from the nostalgic decor. Pick up a Saturday NZ Herald (careful not to strain your shoulder) and check for places.