I would recommend contacting the Canada Revenue Agency (CRA) and asking them how they would like you to treat the payments to your son. Employing a family member is allowed but can cause problems with the CRA.
If you are in Canada or the United States, you can call the CRA at 1-800-959-8281. If you are elsewhere, you can call 613-940-8495. This page has more ways to contact the CRA: Contact the Canada Revenue Agency
Your son can report the income as "Other Employment Income". But if he wants to claim expenses, then he would have to claim the amounts you paid to him as self-employment income.
