The Te Awamutu trainer will saddle Flash Mary in the Kilgravin Lodge 1300 and Whanga Wonder in the Waharoa Transport Co Ltd 1400, and both have proven to be at home in rain-affected ground.
"It shouldn't be a problem for either of them," Sweeney said. "They've both shown that they can handle wet ground.
"I was hoping we'd get the chance to see how Flash Mary goes on a better track – we'd entered her for the fillies' race at Hastings last weekend, but then we needed a change of plan after she drew 17 there. I think it might turn out that she's better on drier ground than this, but the conditions this weekend won't worry her."
El Roca filly Flash Mary made a winning debut on a testing heavy track at Ellerslie in early June, followed by a fourth at Te Rapa and a close third behind Ima Roca Bee and Yeaboi in the Listed Ryder Stakes (1200m) at Otaki on July 31. The fourth placegetter in that race was Bellacontte, who has won the Listed O'Learys Fillies Stakes (1200m) and Gr.3 Gold Trail Stakes (1200m) in her two subsequent appearances.
Flash Mary returned to action at the Cambridge trials earlier this month, finishing third behind Brando and Four Queens.
"I'm really happy with her," Sweeney said. "That was a very good trial, and she's been thriving since then. This race on Saturday should hopefully suit her nicely – after missing the Gold Trail last weekend, there's not a lot else around for her over the next few weeks.
"She's not nominated for the 1000 Guineas (Gr.1, 1600m) at Riccarton, but we might have a look at the Soliloquy Stakes (Gr.3, 1400m) at Ellerslie late next month. That could be a nice race to target if things go well."
Whanga Wonder is also first-up on Saturday, lining up for the first time since early April. The daughter of Proisir performed solidly last season with 11 starts for a win, five placings, a fourth and a fifth.
"She's been super consistent," Sweeney said. "She's obviously a staying mare, so I wouldn't necessarily be expecting too much from her first-up tomorrow. But she's been working really well, and the wet track won't bother her at all.
"I've been very happy with the way she's coming up. She had a trial at Cambridge, where I don't think she was all that comfortable on the synthetic track, and the others probably just went a bit too quick for her over the 950m as well. She's won a jumpout since then.
"She's a versatile mare who's going into this race in good order, but whatever she does first-up, I'd expect her to improve on."
Meanwhile, Sweeney was also pleased with the resuming run of Angaria, who finished second at Cambridge on Wednesday in his first appearance since May. The Niagara gelding has been a leading performer for Sweeney's stable in recent times, picking up three wins and four placings from his 14 starts to date.
"He ran really well the other day," Sweeney said. "Cambridge was a bit of an afterthought for him – we were targeting the first day of the carnival at Hastings, but he drew wide that day, and he also needs a good track.
"We were able to get a run into him on the Polytrack at Cambridge instead, and it worked out really well. He's come through it nicely and I'm happy with him."He needs dry ground, so we'll just wait and see what happens over the next couple of weeks before deciding where we go with him next."