The AT-STs canonically have a driver and a gunner. This means that in this sequence of the film either (a) Chewbacca is driving and the Ewoks are shooting, or (b) the Ewoks are driving and Chewbacca is shooting, or (c) one Ewok is driving and the other Ewok is shooting while Chewbacca sits back and relaxes.

We'll just let you think about that for a minute.

Transcript

Chewbacca: Surely I can drive this thing. I'm an experienced pilot and mechanic.
GM: Well, if you want to play according to the rules instead of what's fun...
Chewbacca: 17. Fun for whom?
GM: Fun for me! Okay, fine. You approach another walker from behind.
Chewbacca: I blast it.
GM: You're driving. You can't man the gunner station.
C-3PO: You mean Wookiee the gunner station.
Chewbacca: Widdle, would you please Ewoc the gunner station?
Widdle: I was born for this!
[SFX]: Pow! Pow!
[SFX]: Kaboom!
Chewbacca: Nice shooting.
Widdle: Just like shooting barrels of fish. With chicken legs.