Biking Resources from Porto on Senda Litoral, Coastal????

Hello to all and thank for this great resource. We're all booked and ready to depart on our first Camino out of Porto in September.
Planning to hug the coast as much as possible - senda litoral with some coastal and also spiritual variante BUT....I'm now having foot pain and realizing I need to figure out plan B which at this point I think means renting a bike... I love biking, but this is not what I'd envisioned - although realize it could be far worse! So, many questions in my recalibration - 1. Recommendations for where best to rent a bike in Porto? 2. What type of bike is best for proposed route? I've found many bikes that I've rented elsewhere are so horribly uncomfortable after an extended ride. My context I'm an active 63 year old female. 3. I haven't located a good bike map (been primarily using Brierley book for planning purposes), but clearly now need a different resource to know if there are limitations on our intended route for bikes as my husband plans to walk. Thank you in advance for anyone who can point me in the right direction!!

Thank you very much for your help. I really appreciate it!