Hi Roger,
Andrew is right, what you need is a media server which will transcode the ALAC files on the fly into something that your other devices are compatible with. I have the same NAS as you and I believe that the standard Synology media server can do this and transcode to PCM - you can install that from the package centre within the DSM interface.
Alternatively I use Serviio (for video, but same principles apply) which has been packaged for the DS212j, and with that you can specify a renderer profile for each device so that it tailors its transcoding behaviour to exactly what that device can handle. There are instructions for how to install serviio on the web and the serviio forum is very good.
Back to your OP, because 'lossless' is just that, if you wanted to change formats then you could convert the files to another lossless or uncompressed format with no detrimental effect. Tools like Max for the Mac will do that, or even iTunes as long as you stick with formats it likes. No need for re-ripping!
hope that helps!
Dan
Edit - just seen your other thread about Twonky. That should enable you to do a similar thing, although the CPU overhead doesn't sound good, so I'd recommend giving the standard Synology media server a go, or Serviio.