Before I say anything -a bit of a caveat. I've flown in Canada, and also worked with universities there, but I'm very far from an expert on the specific question. I'm a Brit with a lot of professional links with the USA, and that's most of my expertise.
Firstly, Europe and the USA have somewhat different views on a degree for pilots. In the USA, a very large proportion of airline employers want to see a degree. In reality however, they don't really value the degree - they are simply using it because they're too lazy to assess the fundamental intellect of their candidates. In Europe, including the UK, a degree is largely seen as an irrelevance, as a piece of paper, for pilot job candidates - the only thing that's really being asked about is the experience and skill level of the pilot, assuming that they are suitably qualified.
The US based "aviation studies" or equivalent degrees being packaged often with CPL courses are generally only of use to circumvent the airline application processes. Educationally, they're extremely lightweight and of no wider value.
There are degree level qualifications that are clearly of real value to a professional pilot. Consider, for example, management degrees, languages, or relevant sciences such as psychology. All of these are real solid degrees that provide learning that a professional pilot may be able to use in the future.
The concept of a "backup" in my opinion is flawed. If somebody graduates in, say, biology or accountancy, then goes off and spends several years qualifying as a pilot, but that doesn't work out. Well, they are then trying to enter the science or accountancy job market with academic qualifications several years old compared to their competitors, and potentially with higher salary expectations. I don't see that as an advantage.
There is an exception - aeronautical / aerospace engineering is a very tough, serious degree. A lot of aerospace engineering employers might be persuaded to accept that the flying was valid professional experience and training, and that there wasn't in fact a career break. However, AeroEng (and I type as somebody with two AeroEng degrees and who has been involved in delivering those degrees in several countries) is a very tough subject, taking twice as long to study the basic qualification as it does to study for an ATPL, and requires a high level of interest in the subject and skill in mathematics and science, to graduate from. So it's a very tough route for a "backup".
I think that if the real interest is a "backup" serious consideration should be given to skills rather than education. The qualified swimming instructor or short order chef might be far better placed in that regard, than somebody with a several years old degree. BUT, this advice should be read the context that in the USA (and thus by extension, possibly Canada) does have this not deeply rational requirement to see a piece of paper saying "degree certificate" at the top to render somebody employable to an airline.
Finally - I'd absolutely agree with the people pointing out that a exceptionally important factor is the question of where your son has the right to live and work.
A note on Embry-Riddle. The university sector does not highly rate ERAU, because it is mainly delivering vocational degrees and has very little involvement with research. or fundamental academic subjects For pretty much the same reasons, the aviation industry does highly regard ERAU - but the best degrees there for a pilot career are probably those delivered to people who have already qualified as aviation professions and are now trying to move themselves into more senior roles.