Sounds fun, although honestly lately my bushwalking expeditions have been small tracks, paved if I can find them as that way I can take my son or the whole family. Especially when you end up carrying the kid 3/4 of the way it gets a bit tiresome.
14km is pushing it!
Although where the Twin Falls is, there is also the Warrie Circuit, I think it's 17km or something and I've done it once before as a kid. I've wanted to do it again for the last few years. Maybe we'll hit it sometime this year?