It is not necessary but if you are staying for 2 weeks not just say 1-2 days then why would you not given SIN would be issued on demand at any Service Canada , possibly at the airport if there is a desk there. Applying later can be an issue for example without a PR card and a COPR older than 1 year and you cannot work without a SIN.
Just put aside time either at the airport if Service Canada is there or at a local office where it will be a simple process to complete showing your COPR and having a SIN doesn’t carry any other obligations but does mean when you return you can start work straight away.