Hello Lee,
What a beautiful itinerary! In La Coruña, Spain I would suggest you take the tour to Santiago de Compostela. It is my favorite city in Spain, I never get tired of visiting it. I have never gone as part of a cruise, but have been there several times while traveling in Spain. It is a gorgeous , old medieval city. The historic center is pedestrianized. Although the Cathedral is the big attraction, the city is full of old stone/ granite buildings full of character. This year is considered a "Holy Year" (because the feast of the patron Saint James falls on a Sunday), so I'm sure it will be more animated than usual.
Bilbao is nice too, the Guggenheim is a must more from an architecture point of view than the art collection it houses. The outside of the building is the most impressive part. Make sure you cross one of the bridges and look at it from the other side of the river. It also has an attractive old town and a big central market. Not sure what excursion to recommend as I have not been there with a cruise. One worthwhile tour could be the one to San Sebastián and Hondarrabia, it is gorgeous there.
We did Valencia as a stop on a Voyager cruise. Unfortunately , we just had a few hours there, so decided to take the Regent shuttle to the old town and tour it ourselves. if you decide to do this make sure you go to the Central Market.