Waiving the tests is at the discretion of the DMV. He's Canadian, so going to the DMV and politely asking to have the test waived while showing his Canadian license has a decent chance of success. "Excuse me, I heard that you can waive the test because I already have a valid Motorcycle license in Canada. Would you, please?" and, if declined, ask if the supervisor might be willing, along with a sheepish "I just really don't want to take that test. It makes me so nervous!"
Manipulate the situation as much as possible! DMV workers are people who interact with hundreds of other people every day. A lot of the people who come to the DMV are unpleasant and make the employees' jobs harder. If you come with a smile, a positive attitude, and all your polite words ready to go, you've improved their day, and people reciprocate that kind of thing.