hello formysons,
go for it, there are many senior peregrinos walking the
camino de santiago. i walked my first camino, the
camino frances in may/june 2012 when i was 69 of age. it took me 31 days.
then i walked my second camino, the camino de la plata during this past winter in february/march in 36 days. i have always walked alone at the beginning to eventually linked up with some camino family at the end. and i have just turned 70 recently.
walk at your own pace, this is your camino. when your feet or your body gets tired, it is time to stop for the stage and get a bed. do not over-extend yourself. you will be alright. you will have plenty of time to get to sdc. you will never be alone in the summer. you will be walking alone only if you preferred to be walking alone.
re the discount on the tarjeta dorada (golden card). this is a card issued by the spanish national railways RENFE, which will entitled anyone over the age of 60 to have a discount on purchase of tickets on spanish trains and cercanias (suburban trains). you will have to purchase the yearly discount card at a cost of 5.15 euros (valid for 1 year and can be renewed annually) by showing your id, preferrably your passport at any RENFE station. this card will entitled you to a discount of 40% on monday to thursday, and a discount of 25% from friday to sunday and any bank (public) holiday.
hope these info are helpful to you. give me a shout if i can be of assistance in any other ways.