MartinR, the the upper, outer levels that are part of the Great Lines Heritage Park, are accessible.
There are good cinder tracks, and slopes rather than steps.
The main slope from the lower car park up to the top is fairly steep: I do not know how the torque of a scooter would cope.
Some of the nooks and crannies to explore have a few steps, but no distance from the main paths, so if you can walk short distances, it should all be accessible for you.
The cinder paths go out to the War Memorial, so that is also accessible on a scooter, then on out over the Great Lines too.
There are plenty of benches and some picnic tables to rest on.
I think you would manage as long as the scooter copes with the main slope.