Hello Vadim, I was aware of changing the permalink structure in WordPress but the problem is their old CMS was really bulky and messy and contained many unnecessary folders and sub folders that I didn't want to recreate on the updated site.
I thought that the best way to do this was through rel=cannonical? So instead of redirecting the old pages to the corresponding URLs I would just need to make sure that each page is under one main URL? I thought 301 redirects were a nono actually. I could be mistaken.