I'm in the early phases of planning a trip to Spain in late April. It will be myself and my partner (both in our 40s) and my 16 year old son. No disabilities or food restrictions. We're considering spending three days in Bilbao or San Sebastian, three days in Picos de Europa, and then possibly 3 or 4 days in Madrid. We'll fly in and out of Madrid and take a train to Bilbao or San Sebastian.
Would you suggest Bilbao or San Sebastian? My son loves beaches, swimming, and generally hanging out on the water. Obviously we won't be swimming in April, but is the beach still pleasant to walk on and collect shells or sea glass? We enjoy art, but I wouldn't say it is a necessity. We enjoy side trips and smaller towns as well.
There are lots of nice beaches in that area. Bilbao does not have a beach, San Sebastian does. We spent time in both cities. Both have a great pintxos scene, San Sebastian has a gorgeous beach and an excellent Basque museum. Both have great old towns. I thought San Sebastian was very elegant especially along the coast. Personally, I'd pick San Sebastian, but others do like Bilbao which does have the Guggenheim art museum.
Close to San Sebastian is Hondarribia which has a an interesting and fun castle complex with great views, also a nice beach.
As you´ll be spending a large part of your itinerary on the northern part of Spain, come prepared for any kind of weather. This is a rainy area and beach weather is not always an option. No shells or sea glass in Donostia/San Sebastian beaches, but walking on it if it´s not raining is a great thing to do. Consider the bus (coach) as well, locals normally prefer it over the train on these routes, it´s faster, cheaper, extremely safe, modern and much more frequent.
Some ideas for your son:
San Sebastion -
Peine del Veinte, (especially the wind sprays) - https://sansebastianturismoa.eus/en/to-do/open-air-sculptures/the-wind-comb/
Plus, a daytrip to Hondaribbia to see the castle and have the ultimate pintxos experience at Bar Gran Sol.
Bilbao -
The Richard Serra installation, Maman and more, at the Guggenheim Museum: https://www.catapult-platform.art/richard-serra-sculpture/
Madrid -
Sofia Reina for Guernica
Dinner at SDD2
Daytrips — walking the walls in Avila, and Segovia for the aqueduct and alcazar.
Picos de Europa -
Fuente De cable car
Whatever you decide, have a wonderful, fun filled trip!