I believe you will have to pick up your permit at Cache Bay ranger station.  Some folks would have tried to get to Kawnipi by night one but I'd think at least one night if not two between Cache Bay and Kawnipi.  I don't fish but see folks at the falls seeming to do quite well.  I'd guess 6 or 7 days?

I'm envious of flying across the Q. Should be wonderful and does save time.