If the mic is for anything besides recording, it’s not going to work.  The Sonos Line-In is not a microphone input (you’d need an adapter).  Even more important, the Line-In is buffered for multi-room transport, so the input has a 75ms lag to build up the buffer and is not suitable for real-time performance.

As to the other uses, they will work.  However, most find a CD player or MP3 player redundant when one can play their own ripped library or one of the many music streaming services supported by Sonos. 

The microphone won’t, for a start. There is a 75ms delay on any Sonos analog input, which makes Sonos unuseful for speaking use. Better to use a non-networked PA system designed for it.

For other devices, the cable box would go via HDMI to a TV, then the TV connects to the Amp via HDMI ARC. Which means the TV needs an ARC port.

You’d need only one Port for the CD player, since the mic won’t be useful (unless your client is willing to deal with the stadium effect of a 75ms delay). And the Amp already has a line in that you could switch to, so perhaps a Port isn’t necessary. The TV and CD player could be both connected to the Amp, and your client would use Sonos’ controller to choose which one is ‘active’.

Sonos can not mix two inputs, either. You have to choose one. 

Thank you for the speedy reply.  I am looking at other solutions at this moment.

I asked when was the last time they used the microphone. They have not touched it in 2 years.

Ran into another problem Sonos needs internet to function and there is no way Enterprise will allow corporate network to be used.

That would indeed be an issue for Sonos. It is really designed for streaming music from Internet sources, and not just a PA or computer speaker.