I've not ridden it but seen parts of the trail as my sister used to live in Clare. It is mainly sealed though there are short gravelly parts (we were staying near Watervale so that is mainly the section I saw). I don't think it looked particularly challenging as it is pretty much flat the whole way though I don't think there is much shade so that would probably make it seem worse for someone doing it with kids, more so if the weather was like SA has been experiencing recently. I don't think I'd do it on a road bike but a hybrid or something with slightly meatier tyres would handle the Riesling Trail easily (I think) :-)
Laterider - Did you end up going as your original post was a while ago. What did you think?