Northen Spain/Southwest France - suggestions please?

[shentodj]

Have booked car on ferry to Santander. We are there for 1st 2 weeks of April, but haven't booked any hotels yet.
It'll be 2 adults + 10yr old son.

Suggestions for Hotels, places to visit etc, all gratefully received.

Thoughts so far are Picos de Europa mountains, but haven't found a Hotel that appeals yet.
could also do a Pyrenees trip as suggested by an earlier thread on here.
What about Biarritz - any recomendations?
What about St-Jean-de-Luz - any recomendations?
Bilboa - what to do apart from Tapas bars and Guggenhiem - hotel experiences?

Thanks in advance,
Shentodj