Yep, it looks like a charabanc. I research (and occasionally write) a fair bit of mountain history and in the years after the First World War through the 1920's there are lots of reports of people hiring charabancs and heading for the hills.
By the late 1930's there are only reports of people getting busses (or for the rock bottom end of the market, the sort of people who stay in backpacker hostels today, furniture vans with light wooden benches bolted down the middle). So from my reading and research, I'd guess that charabancs appear to have died out in the early 1930's.
A couple of years ago, I corresponded with Viv Worthington, the woman reponsible for this site http://www.ansettpioneer.com/
She was quite pleasant and keen to promote the memory of those early bus pioneers. (I think she is descended from them?) She has also written a book on the subject, so if anyone wants to research charabancs, an email to her might be a good start.
Here's a pic from somewhere in Victoria that is on the website entitled "A charabanc with passengers setting off on a day trip".