If you are booking online the site should ask you the number of people and then the price will be given per room.
When my husband joined me on the Camino, we called the lodging directly and asked for a "matrimonial" room. That's not the honeymoon suite
, it just means a bed that can accommodate two. If you ask for a "double" you most likely will get two single beds in one room.
If you're not reserving ahead, still use the same term when you arrive. Albergues may or may not have a matrimonial. Private accomodations should.
In private lodgings we usually asked someone on staff to call on our behalf, using our phone. Every one waved away our phone and quickly took care of the reservation. In an albergue, especially if volunteers run it, the hospitaleros may be too busy to help with so many other things to attend to.
Your Camino is fast approaching. All the best to both of you!