I dont think you need to inform IRCC to the best of my knowledge. when your application reaches to the final approval, they issue a visa so that the applicant can enter to Canada. The visa is a document and if you send your passport with the passport request letter, any visa office can stamp the visa on the passport. In this case, if you send your parents' passport to the Ottawa office with the PP request letter, they should be able to stamp the visas. Not here to confuse you but this is what I feel from my previous experience with other types of visa applications.