We are planning a first trip to Spain next April--Easter week. We will spend the first three days in BCN and then hope to drive up to the Basque region. Ideally, we'd like to plant ourselves somewhere in the Basque area and take day trips from there as we do not like to change hotels/house rentals. Some places we're thinking of seeing while there would be Santillana del Mar and Nacedero del Urederra. Bilbao has been suggested as our base but have also heard good things about Donostia. Any advice on a good base and great day trips would be greatly appreciated!