http://www.bookabach.co.nz is good for holiday rentals.
You might find your children actually want to go to school to meet some other children and to help with settling in. Depends on the time of year you arrive as well. We moved to Wellington just before the new school year started so it made sense to start straightaway (something along the lines of we arrived in Auckland, spent a week driving to Wellington, arrived there on a Saturday, looked round the school on the Monday, bought the stationery on the Tuesday and my daughter started school on the Wednesday. And then changed schools a month later because we bought a house. So anything is possible)