Hey Roger, I have recently returned from our family Camino (Dec/Jan) where most bars/acom etc is at its minimal and we were fine, some days we went without coffee, on the quieter days we would carry some bread fruit and chocolate. But you know the Camino provides and we usually found something open. As Nidarosa said, ask the Hospitaleros for recommendations - they were an invaluable source for us - by recommending where to stay/avoid and also for making bookings for us. Believe it or not, some places do get packed as there is so little choice
We also walked in March 2018 - I was going to start earlier March but worked out that most places were starting to 'come alive' from about mid March so started on the 13th. In short, you will be fine to start off with and as you move across the CF you will find more and more places opening up for the season.
Pagina nueva 1 - not exclusive but a really great resource to have.
Have a wonderful trip. Make sure you have something to keep your ears warm

you wont struggle to find accommodation but may have to walk 20+km per stage earlier on.