I got the xineliboutput working, but it has no mouseable interface. My ancient Dad is not going to remember a bunch of keys without any hints.
I got softhddevice installed eventually using the fnu ppa, but although I get a big black window (on my local machine instead of my Dad's machine, I am connecting via x2go) it displays nothing. It complains about not finding libvdpau_nvidia.so which is not surprising as he has Intel graphics. My machine has Nvidia graphics. Maybe someone can explain what's going on here?
Haven't found a usable vdr-plugin-dynamite yet. The rather scanty github overview page says it "turns the dvbdevices into hotpluggable devices. They can be dynamically attached and detached while vdr is running." That sounds promising but it needs a patch to vdr, which implies I'll have to compile vdr myself. Maybe there is a ppa somewhere that incorporates it, I'll keep looking.
Stopping vdr when he runs kaffeine looks like the simpler option so far. What happens if vdr is recording when he does that? Any way to check for that?
BTW, he's still running Precise, I forgot that I haven't upgraded him to Trusty yet.