I think city breaks are really good especially if you get a hotel with a pool so teen ds can swim etc
We have a teenager and we do a lot of city breaks and I have learnt to plan really well in advance to maximise enjoyable things for all of us - so a mix of things like galleries, museums, old buildings of note, cool restaurants, old bars, walking tours, best ice-cream places, chocolate making workshops, horse riding where possible, swimming, parks, beaches / rivers, shopping - I do a lot of googling before we get there and then make an adaptable plan for each day that hits two or three of the things on the list. Also minimising the travel between these activities.
Works well for us.
DD particularly loved Majorca when we went there - we did 3 nights in Palma in a cool hotel with jazz bands in the bar in the evening, rightin the city centre, it had a roof top pool too. Days were spent exploring the city & swimming in the afternoon, cocktails and nice restaurants in the evenings and a city stroll around the harbour etc
Then we picked up a rental car and headed north to a small fishing village resort place where we stayed in a hotel that was literally across the tiny road from the beach. The hotel had a pool too, so mornings were spent swimming and alternating between the pool and the beach.
Afternoons we headed off in the car and explored a lot of the island which is stunningly beautiful. We visited tiny mountain villages, head a chopin piano recital, walked in the mountain forests, found deserted beaches and had impromptu swims etc
Evenings were spent having dinner al fresco in the village and then a stroll and a drink sitting outside a bar etc
It was very relaxed and we all found things of interest.
We had a similar experience in Madrid - but without the car. city center Hotel had a roof top pool with amazing views across the city so I sat reading / drinking coffee/ wine while dd swam perhaps twice each day - morning and late afternoon. Then out exploring for the day
dd and dh got a train to a mountain village and went horse riding there which they loved. I mooched around galleries and shops. win win