First, a little discovery I made after reading that the BeoLab 5s give priority to a digital coax s/pdif signal over all other signals being sent to it.
That means the BL5s use the s/pdif over the Powerlink audio from the BeoSound 9000, in your case, because of this override.
I have set up my BL5s with a Beomaster 7000 which feeds it a Powerlink signal, and use the Beomaster to channel audio from various sources. But here's the nifty detail - when I choose CD, the Beomaster shifts to CD control mode, and the BL5s accept what's coming down the s/pdif as if it came from a B&O CD-player's s/pdif OUT.
I can control volume, off/on, etc. from the B&O remote, via the Beomaster, and the PL-control connection to the speakers - but the speakers are getting their coax s/pdif signal from a sound card I'm using. This sound card has various connections for digital and analog sources, and I have connected a variety of FireWire, coax and optical Toslink sources to it, including Mac mini; the s/pdif audio out from the STB, etc.
Thus I can use audio from various non-B&O sources, channeling these through the soundcard, while the BL5s think it's all coming from a B&O cd-player.
I use the BL5s in Option 0 when doing this. When I press CD, my setup remain open until I press the standby-button on the remote.
In your case, you have the problem of your system wanting to believe that your CD-player is the BeoSound 9000. This means that when you press CD, it will start the BeoSound 9000 - but if there was a way of assigning that to another function button; and of using the BeoVision 10 as your master, then you should be able to set up a nice system.
Some of the more knowledgeable about option programming etc may be able to help out?
Mac mini outputs digital in various ways: FireWire, USB, optical digital OUT.
I would send the HDMI signal to the BeoVision 10, and let the BV10 do the processing of your movies, sending audio to the correct speakers.
If you can do the workaround I outline above, then all you need is an interface between the Mac mini and the BL5s. I'm using the Konnekt 24D soundcard, which does an excellent job; but there are many simpler ways of getting this conversion done. However, given recent developments in music playback, I would recommend having a FireWire enabled interface to do your translation.
With this setup - you should be able to have your system recognize the Mac mini as one source for movies, and another source for music. I use my iPhone to select music for playback.