To qualify for world championships, each had to achieve four qualifying scores within the last year at registered tournaments in New Zealand.
They will compete as individuals and also together in a mixed team. Randle said she hoped for a top-20 finish in the initial "ranking" round in Yankton, and had set her sights on making the top 10 in the knockout competition.
They may be still in their teens, but Barclay and Randle are already veterans in the sport, having competed at tournaments overseas since they were 12.
Randle, in her first year of design at Massey University in Wellington, was introduced to archery through her family - although at first she didn't think the sport was for her.
"I got into it more when my brother went to the Trans Tasman [championships]. I thought, I want to do that!"
Barclay's reasons for taking up archery were similarly practical: "I need something else to do. I played a bit of rep hockey for the Bay, but through the summer I had nothing."
These days, that summer past-time is his main focus; Barclay opted not to go to university this year so he could concentrate on archery.
He can be found almost every day at the Rotorua Archery Club in Ngapuna, practising on the clubhouse's indoor range when the wind and rain get too much.
Perhaps more accustomed to just getting on with his sport rather than talking about it, Barclay hesitated when asked to explain his commitment to archery.
"It's just ... satisfying."
But Randle was on-hand to expand on this point.
"When you walk up to the target and see all these arrows in the middle, it's great."
Less welcome are the costs involved in top-level archery. The pair said it could cost up to $1500 for a new model bow, and $900 for a set of 12 ready-to-use arrows.
To compound this expense, there was little funding available from the sport's governing body in New Zealand, Archery NZ.
"They pay for your tournament entry fee, but that's it," said Barclay. "Players from all the bigger countries like the States will be funded. It makes it quite a bit harder.
"Until you travel overseas, you don't realise how good the rest of the world is."
Not for the first time, Barclay and Randle will be shooting against the world's best in South Dakota next week.