If your dependent children want to work in Canada, they must apply for their own work permit. Normally, they must meet the same requirements that you do.
In most cases, your dependent children must apply for a work permit for a specific job. Their employer may have to get a Labour Market Impact Assessment (LMIA), a document an employer must usually get before they can hire a foreign worker) from Employment and Social Development Canada. An LMIA allows an employer to hire someone for a specific job.
In some cases, your dependent children will need a medical exam.