In doing a bit more research it looks like trying SPI is doing it the hard way. I2C is a better choice, with Can being the best choice. I havent designed any pcb's yet so this is open, however I do have a working spi controller with spi digital pot working in a different project and I wanted to reuse the code, layout and experience on this new project.
The question again then is, can you sent data to every device on the I2C bus at once?