Santander/northern Spain, recommendations on where to stay please

[Quarepants]

I have two days in Santander in August. I have booked the Gran hotel Sardinero on the beach front in Santander but am now unsure whether that is the best option for us. We are a family of 4 and like to cycle (will have bikes with us) and swim. We are happy to camp, Airbnb or Hotel. Mostly we want to have a great last two days of our holiday before getting the ferry home.

We have been to Santillana Del Mar which is lovely but we dont want to go back there.

Camping Cabo Mayor is within walking distance of a beach, has two pools and is within cycling distance of the city centre.

Also interested.

We had an AirBNB in Comillas for a couple of days last summer before catching the ferry.

We visited the Gaudi house and did a walking tour of the town so all a bit cultural but great after the rest of our holiday.

We also tried to visit the prehistoric cafes but they were fully booked - they were less than 30mins from both Comillas and Santander.