Second Trip to Spain

Consider Extremadura - Trujillo, Merida, Caceres, Badajoz.

Some scenes in Game of Thrones were shot in Caceres so the teens might be interested.

Its’ long time back that I have been to Andalucía thus, I just can drop a few beautiful places I do remember.
Check out one of the Bodegas around Jerez de la Fronteira and add a beach-day in Cadiz.
Have a look at Setenil de las Bodegas, Zahara de la Sierra and Caminito del rey – it’s a save path now (was a rotten no-go, when I was there).
What I really liked was driving through Tabernas Desert and the Cabo de Gata nature park (east of Almeria) but that seems too far away for your timeframe.

Girona is just a 30-minute train ride from Barcelona. It is an ancient city with narrow, twisty, windy, fascinating streets. Game of Thrones was also filmed there for its ancient scenery. There are GOT tours which we did not take. If I were to return, I would take one of those tours, not because of GOT, but because GOT found the most gorgeous spots in Girona. We had a delicious lunch at Blanc Restaurant in Girona. We also went to Toledo which was nice but I preferred Girona.

The Barcelona Cathedral Vespertin rooftop visit at night was spectacular as are all the Gaudi sights during the day.

What a wonderful time for you and your family. What time of year are you going? We just returned from Spain. It was a second visit to Granada and Seville for us. I can't seem to get enough of them. Enjoy!

If you did not visit cordoba last time, then I suggest spending one or two nights there so you can visit the Mezquita. Also the Roman bridge , Alcazar gardens, palacio de viana and wander the juderia.

Barcelona could use an extra night or two.

Since Girona isn’t in the direction you’re headed I’d drop it for this trip and spend more time visiting places between Madrid and Malaga. The cities AussieNomad mentioned are worth visiting and en route, so consider one of those. When going to Toledo get an early start. With only one night you want as much time there as possible.

Depending on the route you ultimately decide to take south, when leaving Toledo, stop at Consuegra for its castle and windmills. There are additional windmills, those referenced in Cervantes’ Don Quixote, at nearby Campo de Criptana. Both towns are off the same road, just 15 minutes apart. Also, rather than stay in Arcos de la Frontera and Ronda each for one night only, consider two nights in Ronda. From it you could drive a loop of the white towns (Ronda over to Arcos and back) and maybe get in some walking in the Grazalema area.

Recommend heading to Barcelona to add the three nights, but use them to explore the day trip opportunities within easy reach. Barcelona offers excellent public transport with ez connection to trains.
Examples:
Montserrat
https://www.barcelona-tourist-guide.com/en/tour/montserrat-spain.html
A blend of hiking, cable cars and monastery make a good menu of experiences. Subway and train connections are easy.
Girona
https://www.earthtrekkers.com/best-things-to-do-girona-spain/
Architecture, ancient walls, well preserved and even some GOT create plenty of opportunities to visit for a day.
The Med
Depending upon the time of year for your visit taking a day, or half day, to spend at the Barcelona beach is an excellent way to relax from your travels. How often do you have the chance to swim in the Med?

The Barcelona area offers a diverse huge menu of opportunities which is why we have visited five times.
Highly recommend renting an apartment to accommodate everyone while having room to spread out and a kitchen to eat some meals.

Many good suggestions have been made, but three nights (2-1/2 days of sightseeing time if you're lucky) in Barcelona is pitifully short even before you start thinking about side trips.