Dependents are permitted to work in Canada. They’ll need an Open Work Permit for this. They will have complete freedom to work full-time in any area of Canada. Except for Quebec, they are free to live and work wherever in the country.
This Permit is only available once they have arrived in Canada. Then, as quickly as possible, they must apply for a Work or Study Visa. Only an Open Work Permit can be applied for by a sponsor with a valid Canada visa.