I have an Adobe Creative Cloud membership and both Lightroom CC and Lightroom Classic installed. I have 3 mobile devices connected to the account 2 iPads and iPhone.
Is it possible to be using all the mobile devices and the desktop at the same time?
Yes, that's fine. If you edit the same photo on multiple devices at once (which is clever!), latest edit wins.
I think I am ok with that my wife does not work with my image files but she is happy viewing and sharing them with friends and family.