I am thinking of taking the train down to Mandurah tomorrow morning and riding/exploring for a few hours.
Probably do at least another 10km around Mandurah. I have done these rides with others who are only occasional riders, those yet to crack free mounts, etc. Biggish distances are not as tough as they sound when you are just ambling, exploring, stopping for nibbles, hopping off to go thru peds, showing off, over several hours.
As well as what we ride around Mandurah, there is a 5k ride each way between station and Mandurah shore. But there are also buses every fifteen minutes if want to cut the distance down. (Yes - unicycles are allowed on buses and is stated so on their website.)
If you are interested in joining me , post here and pm me your number and I'll contact you tonight.