It's possible that the departure gate of the BNE/CNS 717 operated flight will be assigned before you depart SYD so you could Google both your SYD/BNE and BNE/CNS flights to find out both your arrival and departure gate. The 717 currently uses gates 16-18 at the QF Satellite (gates 16-21), gate 25 on the main concourse (gates 22-25) or gates 26-32 at the common user satellite.
The worse case scenario would be arriving eg at gate 21 then departing from gate 26. It that were to be the case ask the crew on the SYD/BNE flight if you can get a buggy ride so the Capt can advise ground staff via ACARS message at the same time they advise if WCHRs are required on arrival.