Dorothy lives in a retirement home but has perfect eyesight and doesn't need to wear glasses. She recently renewed her driving licence so she could continue as a navigator.
The mother and son team have already completed two endurance rallies across the United States and another in Burma.
"I'm a good car sitter," she said. "I love doing all the travelling but I will only go in the Rolls-Royce because anything else is too uncomfortable."
As well as her trusty maps, she also packs plenty packets of tea for the journeys.
"They don't make proper tea in places like America so I like to take my own wherever I go."
Dorothy moved here from the UK in 1950. She is a grandmother of five and also has 10 great-grandchildren.
Of her three sons, Alastair is the youngest. The eldest son Mike died of an illness a few years ago, and the middle son Bill died as a young man in a race car crash.
Former Aucklander Alastair - who runs a successful storage company in England - used to be the boss of racing legends such as Nelson Piquet and James Hunt.
Three years ago he was a consultant advisor to Hollywood film director Ron Howard for the hit movie Rush - about the great racetrack rivalry between Hunt and Nikki Lauda.
Caldwell said his mum is "amazing" and insisted she has the perfect temperament for travelling with. Dorothy said being her son's navigator has brought them closer together.
"We have never had a cross word on a rally," he said. "It is a team effort and we work very well together."
The role of navigator requires a constant state of being alert on difficult routes and often on tough terrain.
But although Dorothy can't wait for the Haka Classic to start, it is liable to be the last rally she takes part in.
"I'm looking forward to seeing a lot of New Zealand I have never seen before," she said. "But I'm now nearly 100 so perhaps it is time to take things just a little bit easier."
