The North Island north of Auckland would be ok all year temperature wise imo ... that includes the Bay of Islands and the Coromandel Peninsula. Should also be ok south to Rotorua and Lake Taupo ... if they rug up they could venture a bit further south to the Desert Road with views to Mt Tongariro, Mt Ruapeu (sp?) and Mt Ngarahoi (sp?), the last one being made famous as Maw Daw in Lord of the Rings I recall.
