If you go to the Black Feather website you’ll find descriptions of a number of Nahanni and other trips. The write-ups - and the additional information if you request it - will give you a good idea of the logistics required, as well as the river running skills involved. Then you have to decide whether you want to organize it all on your own or let Black Feather handle that part of the trip! It ain’t cheap but maybe since it is a bucket list thing, you and your crew can rationalize it!
https://blackfeather.com/canoe/nahanni-river-tripsThe 23-day Broken Skull/Nahanni trip is longer than you want but there is an 11-day Broken Skull that sounds incredible and might fit in with your time constraints and difficulty level. The write-up notes that -
Quote:
The trip is suitable for paddlers with previous canoe-camping and whitewater canoeing experience, but advanced whitewater skills are not required. A warm-up paddling session at one of our springtime clinics is highly recommended!
You can access the Broken Skull write-up here -
https://blackfeather.com/canoe/broken-skull-river