We opted to book the Grand Island Tour which is operated by Australian Pinnacle Tours, the cost of the tour was $99 per adult. This cost is for the Island Tour; the cost of ferry transfer to/from Rottnest Island is additional.
After arriving at the Island and disembarking from the ferry it is about a 5-10 minute walk, depending on how quickly you walk, to the train station for the first leg of the tour. The first leg involves a train ride to Oliver's Hill. Unfortunately on the day of our tour the train was out of service due to mechanical issues. In lieu of the train, transport to Oliver's Hill was provided by coach. Whilst less atmospheric than the train, it served the purpose (the day was lovely and sunny and wind-free; on a windy day, the coach would provide more protection from the elements).
At Oliver's Hill is an old armament, including a tunnel. Volunteer guides take people on a tour, this is in two parts. One part involves descending to the tunnel, there are multiple steps and it can be quite steep. For those who feel uncomfortable with the steps, it is possible to wait and sit out this part of the tour. The second part of the tour does not involve steps, so is fine.
Lunch was served at Oliver's Hill. This included three options, chicken wrap, falafel wrap or salad (the gluten-free option). The wraps whilst fairly basic were fresh and tasty, multiple group members were heard complimenting the quality. Bottles of drinking water were provided. The weather was well-suited to a picnic lunch - there are picnic tables. However, the exposed site means that it could be windy, so would recommend bringing jackets and sunscreen.
Following the picnic lunch there is a tour that pretty much covers the circumference of the Island. Our coach driver was passionate about Rottnest and has been visiting for many years. He provided fabulous insights into the history of the Island and his own experiences. Various stops are made to take photographs, etc.
The tour concludes about 5 minutes walk from the ferry terminal for those who are catching ferries back to Perth/Fremantle.
This tour is recommended both as a way of providing an overview of the Island and for those who may not want to cycle around. The Grand Tour also means that there is no need to wait for the next hop-on/hop-off bus.