I am a member of CRC, great bunch of people, but it is not a high power club. CRC is not Tripoli or NAR but is under MAAC (Model Aeronautics Association Of Canada) and we are limited to G launches. I mostly attend my with kids and we make it a family day, but I still attend it by myself.
If you are looking for high power then the closest club is NAPAS, but we do not have a field at this stage. Beyond that there is a Tripoli club in Ottawa and I believe that there is a NAR club down Chatham-Kent way but I am not 100% on those details or if the club I am thinking of is still operating. I believe they were a relatively new club.
Alternative to Ontario there are HP clubs in Quebec (CAR) as well as clubs in Upstate NY URRG (Tripoli) and MARS (NAR), both of which I am a member of and again a good bunch of people. If you're in Mississauga both the Upstate clubs are roughly the same distance, a 4 hour drive, but well worth it.