I agree with the PP but would take out Malaga for Cordoba.

If you are between Malaga/Sevilla/Granada and Barcelona, I would pick one of the first 3. It'll still be warmer than in Barcelona, and I think since they're smaller they may be more fun with a kid. I loved Granada, it's really not that big and felt very different. Sevilla was nice too, but I've never been to Malaga. San Sebastian and Bilbao are good options too, but I would look up the weather first - I'm pretty sure you can get away with swimming in October in Andalucia, but wouldn't be so sure in the Northern part of the country. Really I would think through though which culture you are more interested in - Barcelona and Andalucia are pretty different in what they have to offer.

We had a blast in San Sebastian with our 2 year old. Hopefully still there - an amazing old school amusement park at the top of a hill overlooking the water. And you take an incline to get up there. And the beach. And farmers markets. And a food crawl, which we all loved. We found a playground or two. Day trip to Bilbao to the Guggenheim, which was mainly for the parents, but the little enjoyed it, too. And we drove across the border into France to visit a few small towns. We had no problem filling a week.

We're finally ready to start traveling post-COVID again and we've settled on Spain -- we have a 5th grader and a preschooler. Plan to fly into Madrid, since we can get a straight-shot flight from IAD to there, and then taking a train to another city for a few days... but which one? My husband says Barcelona, but I've always wanted to see Granada/Malaga/Sevilla (one, I realize we likely can't swing more than that). Which would be best for kids this wide age range? And if we go in early October, will it be too cold to do any beach swimming or outdoor pool swimming... which let's face it, is all my kids really care about doing? Would love any advice. TIA.