O'Leary took some key wickets down at Lincoln University for CD last summer as they finished second equal in the tournament.
Raj will work his 16 players from around the large CD catchment down to a final squad of 13.
He is confident the side will do well as three of them being senior Hawke Cup cricket regulars in Harry MacDonald (Marlborough), Tom Zohrab (Nelson) and Gill (Wanganui).
"He's loving his time here," Raj said of the Canadian, who has been working on bowling eight overs a day at specific spots on the training pitch to "build his load up".
Raj said that Lincoln, in particular the main Bert Sutcliffe Oval, will have hosted five tournaments by the time the Under 17 nationals get underway, including the women's Under 19 nationals as well as the men's Provincial A competition in early January.
This will guarantee a dry and flat track pitch.
"We've picked three spinners and there's five other fast bowlers fighting for two spots."
O'Leary continues to progress in the ranks of a strong Wanganui Collegiate side, having also had Hawke Cup experience for Wanganui, as did his school captain Angus Dinwiddie this season.
"They were all thrown in the deep end quite young. They've been playing First XI for three years," said Raj.
Central Districts U17 will play a pair of two-game games and then four 50 over matches.
They play Wellington twice and the other four associations once each, with at least two games being on the No1 ground.
"That's mean, you get to see your name up on the scoreboard," said O'Leary.
"It's good to get down there a second time. I'm a bit stronger.
"It's nice having a training partner as well."
Gill said when he came to Whanganui he was told by his St Johns Tech skipper Dominic Lock there would be a lot of opportunity to play different forms of cricket.
"It's a really good test, just playing [two-day] long format in these type of conditions.
"I've played that, but we don't have the same skill set for that back home."
O'Leary said there is more intensity for this year's tournament, due to knowing the standard required this time plus having to compete for final spots.