new zealand in a campervan

I am traveling through the south island in a campervan with my family of 5 over the Christmas/summer holiday.
Is important to make reservations for accomodations?
Do the DOC sites fill up quickly?

sell it and buy ticket to australia

Personally I would book ahead at this time of the year to avoid dissapointment at camping grounds throughout the country. Although as thekiwi says Doc sites will usually have space for a campervan without having to book ahead.
To mrsausage: 431 posts and thats the best you can come up with?

hey there
the best thing is to become a memeber of the NZMCA(New Zealand Motor Caravan Assoc). It costs $150 but it gives you some fantastic POP (Park on Property) sites which are generally free. I have just become a member for this reason. Sold my house and bought a campervan, so I could go around NZ and look for the ideal location to buy a backpackers.!! Something to ponder over! Seeya