Great place in Donostia - a few blocks from the beach, and perfect for families with kids: 3 separate bedrooms, 2 baths, and decoration that is very easy to clean and generally safe for kids. It has all the amenities you need (be careful though with the stove, as the pans are finicky) and is close to the playground and park of la concha.
Perfectly located for exploring central, old town and having days on the beach.
Recommend highly.