I truly appreciate the comments about the freedom and flexibility of not booking ahead but I disagree. When I was 20 or 30, freedom meant a lot to me and I didn't want to be tied to any schedule. Now that I'm about to turn 70, I find more joy in the predictable
I've walked the Frances and am just about to start on the Portuguese from Lisbon to Santiago. Putting the issue of injury aside for the moment, I find it very restful to know that a reputable company has booked me into very good accomodations for the night and that I can take my time and enjoy the walk without spending time worrying about where I will lay those weary bones down.
Since, you're only traveling a relatively short distance, I'd book ahead using one of the companies that specializes in Caminos. I'm not affiliated in any way with walkthecamino.com but have used them and like the places that they reserve. There are others that are probably just as good, but I can only speak from my experience. I''m sure that I've lost some of the "spirit" of the Camino but I'll just stack that up with my other limitations as you get older.
Injury is definitely a problem with a set itinerary, but planning your comfort around the possibility of injury seems counterproductive. I know that there are always places to stay on the Camino, but I prefer to know that the place I will stay is good rather than a last minute choice.
Again, I'm not disparaging in any way those who don't book ahead. I wish I could do that now, but the thought of being out of gas (leg-wise) and not finding any accomodation or finding only lesser quality accomodations is much more worrysome to me than a fixed itinerary.
Side note: If you use a company, make sure that they can adjust their itinerary to the types, cost, and style that you want to experience rather than just selling you a one size fits all packaged tour. Also, you don't need anything other than luggage service and rooms. Everything else is just added cost and frills.