To pick up on what littleredcanoe and Peter suggested, the Coulonge would make a nice week-long trip. A possible bonus is that your visitors may be able to spend some time in Montreal and/or Ottawa if interested.
The Coulonge is a nice choice for novice/advanced novice. We paddled down the river from its headwaters last August (15-27) and saw one other canoe tripping party. They were a summer camp group led by two camp staff in their late teens.
Re: outfitters.
Esprit Whitewater located in Davidson does whitewater rafting on the Ottawa as well as canoe trip outfitting and shuttles. They would be able to provide the complete package. Here is their url -
http://www.whitewater.ca/canoeing.htmlYou would have to decide how far upriver to start from so that you could do your seven day trip comfortably. Jim Coffey and Dennis Blaedlow at Esprit have a wealth of experience and can get you sorted out. You could add a day of Ottawa River rafting to your canoe trip. The 12-kilometer run down the Rocher Fendu stretch of the river may be eastern North America's #1 rafting destination!
If you want to get an idea of what the Coulonge involves click on the following links.
Some pix:
https://albinger.me/2016/09/04/canoeing ... to-ottawa/Intro, Planning, Maps, Day by Day reports:
https://albinger.me/2016/10/20/canoeing ... ning-maps/