Could you post your grade 10 program as well as any other works (grade 9 and higher) that you have learned. It would help give a better idea of what repertoire to pick.
If you want to avoid overdone, do the Clementi instead. Or ask to substitute a Czerny or Weber sonata.
Unfortunately, the RCM examinations system isn't that flexible when it comes to sonata choices for the list B
The Weber c major sonata (4th movement) is on the list as an etude ...