Kennedy, who officially announced his candidacy on Monday, was education minister under McGuinty between 2003 and 2006.
He stepped down to make an ultimately unsuccessful run for the federal liberal party leadership.
Kennedy appeared on CBC Radio's Metro Morning on Monday and said he will bring "different approaches" to the party, among them moving away from the current government's decision to use legislation to settle labour negotiations with teachers.
Liberals passed Bill 115 in September, which imposes a contract on teachers and gives the government the power to stop strikes or lockouts for two years.
“I don’t need legislation to get labour deals," Kennedy told host Matt Galloway on Monday. "If it’s one size fits all, that can’t happen.”
Kennedy also said he would consider repealing the bill.
“If scrapping the bill would be the key thing to doing that, I have no compunction about doing that whatsoever," he said. "There has to be a fair negotiation.”
Kennedy also said he would not wait until he holds a seat before starting a new legislative session.
In a controversial decision, McGuinty prorogued the legislature on the same day he announced he was stepping down.
"We can bring the house back, we can start solving problems," said Kennedy.
Opposing Kennedy for the Liberal leadership are MPPs Glen Murray, Charles Sousa and Kathleen Wynne. Sandra Pupatello, a former Liberal cabinet minister, has also launched a leadership bid.
Eric Hoskins, MPP for the Toronto riding of St. Paul's, is expected to announce he is running on Tuesday.