My daughter (Faith) and I recently walked this route, we are both vegetarians, and had no problems at all. One of the simplest options is to stay in alberges with kitchens (check there are cooking utensils). We made friends with several other walkers, and many nights would all cook up a communal meal, when the others wanted meat with their meal, we would usually divide it up into veggie and non-veggie, by making two sauces. The camaraderie around these meals are some of my favourite memories of the walk.
As suggested above, bread, cheese, a handful of olives and some fruit are easy to buy and make for a good impromptu lunch anywhere along the route. We didn't expect to generate such large appetites through walking, and Faith who is normally a very fussy eater, remarked how good things tasted after a few hours on the camino, and invariably chomped anything that wasn't nailed down!
Specific to you request for places to eat, when you get to Santiago, head for "EntrePedras", Hospitalino, 18. Its on the edge of the old city, a few minutes walk from the cathedral and a great watering hole for veggies. The meals tasted great, huge portions and a nice atmosphere. We discovered it by chance, but liked it so much we ate every evening there for the three nights we were in Santiago. Wander down the street and get an ice cream afterwards and enjoy the atmosphere in the streets, makes a great ending to the day and your camino.