A blood test showed Nugent had 116mg of alcohol per litre of blood. The legal limit is 80.
When spoken to by police, Nugent said he had swerved to avoid another car.
Defence lawyer Stephen Ross said Nugent's son was restrained in a booster seat, but "for some reason the booster seat was not tied into the vehicle".
Nugent thought it was, Mr Ross said.
"There may be a suggestion that his son has fiddled with the restraint," he said.
Nugent admitted he was driving about 55km/h.
He said he had just read a text and was putting his phone down when the accident happened.
Nugent has a dangerous-driving conviction from 2011.
Judge Chris Sygrove remanded him to October 13 for a pre-sentence report.