Hi Sandra
We have just had a similar experience looking for Vets open on Sunday for the Monday Sailing from Santander and like you we have two dogs. Our experience was that Vets in the Ferry area were quite expensive, having a captive audience as it were, adding a further 30 - 50 euros for opening on Sunday on top of 22 euros per dog for the consultation. Fortunately we were able to have our pre-embarkation check up and treatment done at the local vet near where we were staying (We were just south of Cadiz) on a Saturday MORNING. It's well worth asking locally, do it well in advance of sailing, as some Vets are willing to 'stamp' your passports with a post-dated time. i.e. Our appointment was for 10.00 am but our passport was timed at 17.30hrs. The biggest suprise was the fee. 12 euros for TWO dogs, yes, that's right TWELVE euros. We supplied the treatments, but even so an amazing saving. Having said all that it's probably a good thing to keep the details of the Vet in Santander, as a back up, just in case you can't find one locally.
For a Campsite try www.cantabria.com/complejosantillana Animals accepted and near the medieval village of Santillana del Mar (well worth a visit)Open all year and about 25km from the Ferry. It's also a Camping Cheque site.