My biggest concerns are the unknowns: will I succeed
Six years ago I had much the same qualms: encapsulated with in the expression "would I fall over on the first day?" and have to return home "with my tail between my legs".
Some suggestions, If I may, for your consideration. These come from my four years of training before starting out and from the time since my first footfall in Le Puy-en-Velay in April 2016.
My plan was to be like the tortoise that (almost) didn't stop, once started for the day.
My training included working up to achieving 30 km per day with all the gear I would carry. This also helped to shake down what was necessary.
I quickly found to dress for the middle of the day and not for the apparent chill first thing in the morning. Fingers were my most sensitive part and so I wore gloves: put them in side pockets as soon as they were not needed. Typically I started with a short sleeve merino top - if the wind was supper strong I would add either a long sleeve merino top or a parka (rain and wind-proof. )A fourth layer, if needed, was a below the knee rain coat with hood.) When I eventually started from Saint-Jean (on the 1,200 metre elevation gain) I saw so many pilgrims stop, take off their pack, take off their long sleeve tops and put them in the pack, pull out a short sleeve top, dress, close up the pack and carry on, possibly getting a chill while stopped.
Another thing I found from my training was, as the way ahead steepened, to shorten my step - the steeper the gradient the shorter my step - on the steepest sections the heel of one foot barely got to halfway along the other foot - and breath in on one foot fall and out on the other. While slow to me, I noticed I passed so many and was passed by so few that morning.
Of course, that is what worked for me: you will develop what works for you.
I wish you and your husband well, saying kia kaha, kia māia, kia manawanui (be strong, confident and patient).