accommodations in april

Welcome to the forum.
That early in the year I doubt very much that it would be necessary to book ahead. I seldom bothered last year in July (which is far busier).
However you might want to check on Gronze as to when the Albergues are going to open. Or even direct if you have somewhere specific you wish to stay.
This year for example many only opened shortly before Easter. I'm not sure if this is a traditional pattern or not. If so, remember Easter is 3 weeks later next year (20/4).