They do recognize naman any certificates galing tesda or any other trade school but hands-on experience is the most important especially if your boys want to sit for a red seal(journeyman) exam. To be elligible for that exam, one must have a minimun of 7200 hr(approximately) of work paid experience and must pass the assessment procedure. And if they passed the red seal exam, then they can work anywhere in Canada and their license has no expiration(lifetime). Almost all trade occupations in Canada are regulated in Alberta and in Quebec but voluntary in other provinces. But most of the company especially the big ones(mining/oil and gas) prefer hiring journeyman trade people with a higher rate plus benefits.
But if they really want to learn trade jobs, they can enroll in Canada instead. While studying, they can work as apprentice trade person and earn a decent amount of money.