As a Sole Proprietor wanting to add employees, you will need to set up a Payroll Account with CRA and follow the CRA rules. This means you will need to make monthly remittances to CRA for deductions such as CPP, EI and Income Tax.
Note, as you are hiring your son, special rules apply and you likely will not deduct EI premiums for him and he will not get any EI Insurable Hours.
Please see these links from CRA:
CRA - Payroll
Not dealing at arm's length for purposes of the Employment Insurance Act (EIA)