Mrs Tairua (46), a farm manager from Hillend, near Balclutha, and Carl (24), who works on a sheep and beef farm at Dunsandel, have both qualified for the championships.
It is likely the pair could be the only mother and son combination at the event which begins on June 7.
The two will not be rivals as Mrs Tairua has qualified for the heading events with Ghost, and her son has qualified with huntaways Rum and Hood.
"He's going to have to support me and I'm going to have to do the same for him," she said this week.
Before her late husband, Jery, and she decided to get into the sport together about nine years ago - "it was something Jery and I could go and do together" - Mrs Tairua's only foray into dog trials was when she competed at Wyndham when she was 15 and came second in the maiden with a huntaway.
She has only got more serious about trialling in the past five or six years.
Her dogs played an important role in her everyday farm work and she confided that she did not like training very much.
"I don't have the discipline to train. Jery used to drag me out to train."
Since her husband's death nearly four years ago, she had been "slacking around", she said.
While the husband and wife had been good training partners, rivalry was always fierce when they went to trials and, if she had a better run, "you had to rub it in".
"Men don't like being beaten by a woman. Sometimes that's the best part," she laughed.
Her husband would have been "stoked" with some of her successes, including a fourth placing with Bump in the New Zealand final of the Tux yarding challenge at Pio Pio last year.
Jery Tairua got Ghost as a pup, from Nick Anderson in North Otago, and Mrs Tairua trained him.
Ghost is now 4 so she did not have high expectations for him at Gore, saying "he really needs another year or so", but he had improved at each trial he had gone to this season.
Mrs Tairua has not previously competed at the national championships, while Carl ran Rum at the 2008 nationals in Blenheim.
He bred both Rum and Hood.
It was "only really sinking in" that the pair would both be competing at the championships and she said she would be surprised if there were other mother and son combinations competing.
While she had great support from her local area, she expected there would be some nerves.
"There's a few old fellas quite keen to see how my dog goes.
"I'm already getting texts saying, I hope you're out there training and hope you're doing this' ...
"That's where the pressure's going to come from," she said.
