That should not be impossible!!!
But it depends on, what you want to use the NAS or rather the server on the NAS for.
Since you write about 'iPhone/iPad' I assume that you use iTunes for music.
If the NAS has an 'iTunes-server' running you can control the playback of your music to an AppleTV or any AirPlay audio device (Playmaker, Essence...) with the Remote app from Apple. And you can AirPlay Netradio-stations etc from the iDevices.
In fact a MacMini would do as 'server'.
If you want to distribute video, it really depends on the format of your videos....
In case you use an Apple-friendly format, the AppleTV should do the job.
If you need other fileformats (MKV...), you will need a DLNA compatible server on the NAS (or on the MacMini depending on how much space and/or if you need a raid system for security). 'Twonky' as full version is the server, which B&O recommends, but there are others.
With the BV11 you already have a DLNA player built in (which can play video and of cource also music and pictures from the DLNA server on the NASMacMini).
The MediaPlayer of the BV11 will probably very soon be able to act like a 'renderer', which means that you can control it from an app on the iPad...or rather that you this way can 'play-to-it from the app/the control point.
Otherweise the ATV will do fine for an iTunes library or for AirPlaying.
If you want to distribute sound over MasterLink from your main Master (the BS9000) just connect a Playmaker (you can still get them) to the A.Aux-in.
The 'BL17' in the child's bedroom' probably are connected to a BeoLink Active. This has a PC-in port You can connect a Playmaker or an AirPort Express to that - and use that source locally.
The BeoVox 2-2 probably are driven by a BeoLink Passive. If you get a extra BL Active (with the ir-eye connected to it) and use the BL Passive as an amplifier connected to the PL-out, you could use the PC-port of it as described above.
If I rember well, the Amp for the BL15/16 has an imput for a source - again, here a Playmaker (or an Essence) would do the job - best ask your dealer.
This would be possible as a wireless setup (with the right router with the correct settings). None the less I would suggest using cables whenever possible.
As you may have noticed this setup would involve a great deal of knowledge. If you want to do it yourself, you must get familiar with what is possible with AirPlay, DLNA and the needed devices and servers.
Otherweise you will need a skilled B&O technician - some of them will surely be able to work this out. And maybe they will come up with some other (better) ideas, when they have had a closer look at your B&O infrastructure.
Greetings Millemissen