Instantaneous Transmission, Selective Response
Would this idea work...


It should, provided the interface requirements are met (SPI fanout?) and the devices can handle the data rates. 


  ...or is their a better solution?


Possibly, but why should you care? The important thing is to develop a solution that works satisfactorily. An advantage of your idea is that it is simple and easy to debug, whereas a 'better' solution that eg. multiplexes the SPI slave responses might require extra hardware and more complex software that could be hard to get right.