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I've fallen with the canoe twice, once when I was 16, once when I was 50 (my next scheduled fall with the canoe will be when I'm 84.) The one that happened when I was 50...I hadn't thought of this until SS's post, but it was very similar to the way I fell in September. When I was 50, I rolled my ankle on a very small, nearly invisible nub of a root on a cart-path-wide portage, on level ground, and I just crumpled. The difference was just the direction my ankle rolled. With the backpack, I've gone down a handful of times over the years, almost always in a controlled way where I can kind of sit down. Still, I think about some of the portage terrain....I've tried to be careful, but it can happen so easily and so quickly. I'm 60, I still have some canoe tripping ahead of me, but I'm going to take this like a bit of a wakeup call. Had I done this in the park....what a mess. What an absolute mess. Would need help getting out, stuff would be abandoned until somehow it magically gets retrieved, I'd unable to drive home the 6 hours or whatever home, etc. What an absolute, total mess that would be. Plus it hurts to do it. A lot. I'm still in PT, 2 months later I am walking without a crutch, but I still limp. Still a bit swollen, still lack full range of motion...I've made a lot of improvement, but am still a work in progress.
The thing is, I'm not ready or willing to hang up my paddle. We all acknowledge the possibility of injury when we push off from shore. I wiped out in my back yard, not on a canoe trip. Injury like this can happen anywhere. I've always tried to be careful about injury-risk on my trips (not rushing, taking care on bad terrain, not overloading myself, etc.), and now part of being careful about injury-risk will include route selection.
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I'm only 3 years behind you, so I can appreciate the decision/planning you are making. Definitely don't hang up your paddle, but at the same time at a certain point you don't need to climb Mount Everest, climbing a smaller mountain will do. Life is a continuum, at some point just making it to the toilet without falling will be deemed a success.
Up until a couple years ago when my dad was in his late 80's I still managed to get him out to do some camping/paddling/fishing by taking advantage of the water taxi on Opeongo. At some point it becomes more and more prudent to cut back the adventerous expeditions. Pure paddle in trips have their advantages, reducing fall injuries, and as you alluded to much easier to extract yourself in case of injury, no buggy portages, open lakes have very little bugs, you can more easily bring more comforts of life, etc. Pure paddle in trips and/or water taxi, helps to extend the adventures.
FYI, I do work in a rehab hospital and there is a reason we don't have many young patients (I'll say anyone under 60) and certainly almost no one in their teens/twenties/thirties/forties unless it is due to a traumatic motor vehicle accident. I also recognize that patients that are not motivated to recover, don't... having a reason/goal to push yourself to recover, do your PT, exercises, etc is also very important. Good luck with your recovery! Whatever you decide, stay safe! Trust me... I already have plenty of job security, I don't need any more customers 
