The sidecar will put your butt closer to the track. The motorbike will give you a higher view. They will be different experiences, but only slightly.
I think scene 12 is more likely, directly after the devils snare. That will be the most Forest-y part of the ride by far so it fits. Scene 9 is already cluttered with fluffy prior, then Anglia, then spike. But that’s just my guess. Centaur could be in the queue as part of today’s lesson like in the book or even scenes 2 or 3 at start of the ride for all I know. I haven’t yet heard where he will be. But 12 feels right.