Hmm. If you are keeping the Mac mini in the chain, that, of course will work fine. Plug it's USB out into the CA and you are good to go. As long as the Mac can see the NAS, you are fine. It should recognize the CA. Macs are good that way.
If you want to take the Mac Mini out of the audio chain and use the NAS you would be better off running a music server program. I don't think the Cambridge can browse the network and read drives - it can only do that if the music drive is connected by USB. But that's an option. Get a small portable SSD drive and copy your music onto it. Plug into the CA USB port. Cheaper than a NAS.
HOWEVER, a music server setup on a NAS makes it far, far easier to browse your collection. Using only a USB drive you have to navigate your directory structure and choose files. It won't play albums in sequence, do gapless, or any of that fun stuff that makes it easy. If you are a classical buff, get Minimserver and tag your collection. If not, just use Plex, or Emby, they make it easy for all the other genres, supplementing the metadata from the web. Both come with a Qnap or Synology, and take five minutes to set up. Then the CA app on your iphone will see your music collection and let you browse it by album/genre, etc.
@recluse- The CA app has built-in capabilities for streaming radio - you can browse by genre, resolution, country, etc., and save your favorite stations to a preset.
The CXN is a *very* versatile streamer. You will be able to do most anything you want, especially now that they also have built-in Chromecast, which will allow you to play to the CA directly from the Tidal or Qobuz app. Spotify will see the CA natively. There are other versatile streamers, but they are either more PC-geeky (Raspberry Pi implementations) or overpriced high-end that isn't likely to sound any different to you. This is not the place to spend the bulk of your hifi money, IMO.
Finally - wifi. I prefer to run with ethernet to the CA streamer. I have a great Ubiquiti wifi setup, with huge bandwidth, but there can still be dropouts and gaps. There's nothing like the solidity of a wired connection. The control point can be over wifi, since that is just passing commands and file locations, but the path from the stored music files to the CA streamer is better wired, IMO.