While Gai Waterhouse anticipates success on the racetrack on Saturday, the champion trainer's excitement on Friday was on the family front.

Waterhouse's daughter-in-law Hoda and son Tom welcomed their second child, a baby boy, on Friday afternoon.

"They had a son. I've now got a grandson," Waterhouse said.

"It's their second child and first boy.

"All are very happy and well, and congratulations to them."

The youngest member of the Waterhouse family has been named William Waterhouse.

The trainer will remain in Sydney for Saturday's Run To The Rose meeting where her runners include Raphael's Cat in the main event, but Waterhouse will keep a close eye on the Memsie Stakes meeting at Caulfield where she has three runners.

Dual Group One winner Cosmic Endeavour resumes in the Cockram Stakes while Cups hope Excess Knowledge steps to 1700m second-up in the Heatherlie Handicap.

Waterhouse also has Giulietta in the Montague Tree Handicap (1400m).

The trainer decided to start Cosmic Endeavour's campaign in Saturday's Group Three Cockram Stakes rather than the Group One Memsie (1400m).

"It's an easier race," Waterhouse said.

"It's against mares, she's very well-weighted and I just thought the 1200 metres was what she needed first-up and not the 1400."

Cosmic Endeavour, who arrived in Melbourne on Tuesday, has Group One wins in the Tattersall's Tiara last year and the Canterbury Stakes in the autumn.

Waterhouse said the mare was "ready to rock and roll" in the first start of a campaign aimed at the Myer Classic.

"She's the best mare in Australia. All the others have been retired or they are not as good as her," Waterhouse said.

"She's quite a versatile mare but you would think that the Myer Classic has got her name written all over it, wouldn't you?"

Excess Knowledge was beaten two lengths when fifth in the PB Lawrence Stakes (1400m) first-up and Waterhouse said she was confident his campaign aimed at the Cups was on target.

"Whatever he does tomorrow he'll just be fitter and better for his next step up, but he'll run a huge race," Waterhouse said.

"He's the horse to beat. He'll fight out the finish and I couldn't be happier with the way he's come through his last run."