Just ran it this year from July 28th to Aug 10th but we started at Rabbit kettle Lake.
The lower rapids are easily avoidable in such a large river and are not the primary reasons to go on this trip.
Another great read for history/background of the Lower Nahanni is "Dangerous River" by R. M. Patterson.
I did find another book but will have to reply later with the title and author.
Consider the water taxi out from Nahanni Butte if the weather turns bad, due to limited campnig areas and slow current in a huge river.
Takeout at Black Stone with nice camps and possible vehicle parking.