You want mpd to server and play the music, connected with a web front end (there are a few to choose from) accessible on the private store wifi. You should probably serve this frontend only to a certain machine on the network (like the managers computer in the back) and lock everything else out. The last time I ripped CDs on Linux I used whipper, which I believe was the successor to morituri. This is all only legal if the CDs they have already included the licensing fees to play them publicly or are themselves freely licensed. There are sources of freely licensed music out there that you can play publicly without paying.