While many young players are already swinging a racket by the time they reach intermediate school, both of these lads were in their early teens when they had their first hit with the little black ball.
Male parents were involved in both cases, Cooper following his father into the game, while Grindrod and his dad shared a trial hit on a whim.
The final team for Qatar was named following three selection tournaments: last month's Wellington junior open and New Zealand junior open, and the Waikato junior age group titles on May 11-13.
Alongside Grindrod - a member of Tauranga's Devoy Squash & Fitness Centre - the playing spots are filled by national junior No1 Jonny Barnett of Hutt Valley, Todd Redman of Hawke's Bay and Kapiti's Zac Millar.
Announcement of the team, coached by national high-performance coach Paul Hornsby, brought mixed emotions for Cooper, the 17-year-old Mount Squash Club member admits.
In the crucial Waikato tournament he had gone down to eventual winner Millar in the quarter-finals.
"It had been so close throughout the tournaments, I was nervous.
"Paul came to me before the announcement and told me I wasn't in the team ... I was gutted, it seemed all the hard work had been to no avail.
"Then he said that because selection had been so close, for the first time ever, Squash New Zealand would take five players to the world juniors instead of four, if I accepted going as reserve.
"Obviously I'm disappointed I'm not going to play in the team but I still get to represent my country and I wasn't about to turn that down. It was a pretty easy decision really."
Kicking off on Monday, the Milo All Star junior open runs till June 2 in Kuala Lumpur, followed by the five-day Penang International junior open from June 4.
With divisions in two-year splits from under-13 to under-19, the events draw up to 900 players.
For Grindrod, aged 18 and a Tauranga Boys' College student, making the final cut for the side was a matter of sticking to his natural game.
"It was great to get into the squad. I could beat most of those [eight] guys and from there I knew if I trained hard and didn't do anything stupid I could be in the team," Grindrod said.
He was knocked out in the under-19 quarter-finals at the Milo event in Malaysia last year and placed fifth at the Penang event.
"I learned a lot on that trip, there were so many players from a big range of countries.
"The Malaysian and Pakistani players have great racket skills, they're really inventive," Grindrod said.
Ranked No2 nationally in the under-17 division since last year, Cooper placed in the top-20 at both Malaysian tournaments in 2011.
To blood the squad, last year's Malaysian foray was preceded by a trip to Sydney for the two-fixture Australian Junior Series, where Grindrod finished third overall and Cooper in the top 10.
Both boys graduated to A2 grade late last year.
Cooper remains the country's second-youngest A-grader and rates last year's overseas excursions as invaluable to their development.
"There's a whole new environment and climate, and you get to see how other cultures act both on-court and off. It has been a huge experience."
Last year Grindrod played in the Bay of Plenty senior team who finished fourth nationally.
At scholastic level, he is out to go one better with the Tauranga Boys' team, who finished third at the national secondary schools tournament in 2010 and runners-up in 2011.
He won last year's final and made the tournament side on both occasions.
The national junior side will train intensively in Auckland for a week before departing for Qatar's capital, Doha, where the world junior individual championships will be held from July 7-12, followed by the team titles from July 13-18.
Egypt have dominated in recent years, sweeping the medals at the 2011 individual titles in Ecuador and winning 11 of the 13 team events held since 1994.
New Zealand placed sixth last year and have only made the podium once with bronze in 1980.