If it is the dancing that you are most keen on seeing, check that there will actually be some dancing at the show. Normally the performers will be listed on the flyer - 'Baile' is the dancer, 'Cante' is the singer, and 'Guitarra' is the guitarist. 99% of tourist-orientated shows will have all three.
The flowery dresses seen in the tourist brochures are only for very special occasions (and touristy performances); much of the time the dancers are dressed in black.
And I have only ever seen a flamenco dancer use castanets once!