There's a 9 am mass at the Parish of Santa Maria del Juncal, 1.5km from the albergue. There is also the Guadelupe Shrine, 4km along the Camino toward San Juan de Pasaia, but I have no idea what the hours are. Another possibility is the Church of Saint John, in San Juan de Pasaia/Donibane Pasaia which is 17km out of Irun-- again, I have no idea of what service hours might be, but if you arrive there about 10 or 11 (not impossible if you start quite early) then you'll likely land in the middle of the parish mass. It's possible that the turismo (
turismoapasaia@oarsoaldea.eus) might have an idea of mass times.
I'll wager that pilgrims coming off the trail into Easter mass will be well-received. San Juan de P is a delightful little village and highly recommended for a stop. The albergue is small but looks comfortable. Senora Ione kept a lovely pension (Txurdin) quite close to the albergue, but I am unable to figure out if it is still open in the post-pandemic period-- the number is +34 685 47 57 33 and she is on WhatsApp -- she speaks no English so you might want to plan your conversation carefully beforehand or have a hispanophone friend call. I understand that there is AirBnB accommodation in the village but, after checking, only one of the 4 available has an opening for Easter, which is an insane travel period for the Spanish.