ADuM3154 application that requires isolating two SPI slaves

1) What is the recommended approach when using only two slaves? We have two /SS pins available from the host MCU. It looks like we should connect the first slave select to /MSS, the second to SSA0, and fix SSA1.  

 

2) DS table 18, suggests that MI is driven even when the chip is not selected; if we want to have another device communicating on the line, we need to power down this chip to avoid contention on this line. Can you confirm this is the case?