I spent a week in El Puerto de Santa María (south of Seville) with two kids last summer and we had a wonderful time. Granada was fun, but that was because we loved the Alhambra. Too bad.
Do Jerez and the horse show. It was wonderful and we enjoyed the time on the grounds before the horse show even more than the show itself!! The train stain has beautiful tiles!! Osbourne does a great sherry tour in El Puerto and my kids thought it was cool!! Cadiz offers more options. Huelva and Parque Nacional de Doñana are also options. There is plenty to do in that area.
We then flew from Jerez to Barcelona for about the same price as the train!! I would not do Tangier. Also you have Los Arcos and Ronda near by. Rent a car or use the trains and buses. We spent two days in Ronda and loved the caves located outside of town.
Don't feel like every moment has to be scheduled. Things just come up and fill the days!! We met folks from England on the Osbourne tour and they took us sailing on their 45 foot sailboat one day.
It was ALL incredible!!!