Hi Rebecca,
Yes, you can split this stage in two and spend the night in Boimorto.
From Sobrado dos Monxes it's 22 km. to Boimorto.
In Boimort you can stay at Albergue de Peregrinos de Boimorto (newly built, only a few years old), phone number 638 392 024.
From Boimorto to Arzua is 11 km. But, at the albergue in Boimorto they have information about an alternative route (including a description of this alternative route). This one joins the
Camino Frances halfway between A Salceda and A Brea (about 8 km. after Arzua). The alternative route is a bit shorter than walking from Boimorto to Arzua and then to A Salceda/A Brea. Although this alternative route means walking on (quiet) asphalt roads, the advantage is that you get to spend more time in the quiet countryside, before joining the crowded
Camino Frances.
Taking the route from Boimorto to Arzua, possible stages are:
Boimorto - Arzua - A Salceda, 22,3 km.
A Salceda - Monte do Gozo, 23,3 km.
Monte do Gozo - Santiago, only 4,9 km. which leaves you plenty of time to be in the cathedral in time for the mass.
Taking the alternative route from Boimorto, possible stages are:
Boimorto - Santa Irene, 23,6 km.
Then either Santa Irene - Monte do Gozo 17,7 km. + Monte do Gozo - Santiago 4,9 km.
Or Santa Irene - Santiago, 22,6 km.
Possible albergues:
Arzúa: various.
Boimorto: Alberge de Peregrinos de Boimorto (only a few years old), phone number 638 392 024.
A Salceda: El albergue de Boni, phone number 618 965 907.
Santa Irene: Albergue de Peregrinos de Santa Irene, phone number 981 511 000.
Monte do Gozo: Albergue de Peregrinos de Monto do Gozo, phone number 981 558 942.
Santiago: plenty.
Hope this will help a bit.