One thing to keep in mind: aerospace engineering is a specialized form of mechanical engineering. Consequently, many of the engineering programs in Canada will offer mechanical programs that have an aerospace option or aerospace specialization that amounts to a few extra courses here and there. There have been numerous threads that elaborate upon the differences (see the Academic Advice forum) and get more into the details of the profession (in general) so if you want some of that, you can track down a few of them using the forum search.
A second thing: modern planes, space craft, and satellites are extraordinarily complex pieces of machinery that require thousands of people, millions of person-hours, and billions of dollars to design. They also involve nearly all disciplines of science and engineering (not to mention soft sciences: how do you design aircraft that people will be able and calm enough to evacuate in case of an emergency?) In that sense, many (non-aerospace) engineers have worked in the design of aircraft systems (and sometimes, depending upon their training or expertise, even in the parts of the system that make it fly, or at least the modeling and/or simulation of them).
As for accreditation, any of the Universities accredited by Engineers Canada (they're the umbrella group for all the provincial organizations) will deliver a high-quality education that satisfies their fairly rigorous requirements. That, and there are very few fly-by-night higher-education outfits here (as compared to the US, for the simple reason that there are a whole lot of real and legitimate ones)--as a Canadian, you'll usually recognize Universities pretty quickly (the only one I hadn't heard of by the time I graduated was Lakehead University). We're lucky that the quality of undergraduate education is fairly uniform in this country. Research opportunities, extracurriculars, etc. all vary, but that's a different matter.
Now then, generalities aside, I am not an aerospace engineer. My understanding of the engineering profession, and engineering landscape in Canada (YMMV--Your Mileage May Vary) is that you get hired based on your experience (what you've done at previous jobs), or, if you're a fresh graduate, whether or not you've had relevant-ish education (very rarely will you have exactly the skills and training to do exactly what an employer is looking for). So while you might not hire a freshly-graduated Chemical Engineer to design a jet engine, you might hire a Mechanical Engineering grad to do air intakes or help model wing stress.
So, I'd figure out what you want to do with aircraft (design? maintenance? piloting?) and then start sending out e-mails to the Aerospace or Mechanical departments of the Universities you've got in mind, and start contacting companies you think you might like to work for and ask what sort of educational background they hire in--who knows, this might lead to actual employment (down the road, of course) or at least a chance to tag along for a day or two and see what it's all about. Your high school may have someone that can help you with these, so I'd also take a look into this.
Good luck!
