Greetings, Tom.
We have been in that area many, many times.
There are at least 4 camp sites on the east end of Beaverhouse that you can use for backups. 2 of them are west facing beach sites, one is on the large Island east of the ranger and 1 is on the west facing point on the N shore near the Q river. On Q lake, there are quite a few sites in the Eden Island vicinity. Think E and W facing points. Once you get beyond the Eden Island area, there are just a couple of sites in the narrow part of Q lake, until you get towards the East end of the lake.
Another route option would be to go up into Cirrus then Kasakokwog to McAlpine to Pickerel. Sue falls would be a don't miss on this route. There are some good cliffs on Cirrus with deep water under them for jumping off of. I have graphed 300 feet of water in Cirrus Lake. (Deep enough to drown in.)( My kids used to freak out when I told them about really deep water that we were passing over. )
Fishing is great on Cirrus as well as most of the lakes in that area. Lakers in Beaverhouse, Q, Cirrus.
Port between Cirrus and Kasakokwog is fairly long and hard, good size hill. There are some nice sites on Kasakokwog. Traveling W to E, should give you tail winds on the large lakes. The nice thing about Cirrus is that it is off the main travel routes that are heading east. We spent 3 nights on the middle section of Cirrus in July 2008 and saw not one canoe.
All of the various route options that you mentioned, I have done with my wife and kids. Some of them the kids were very young and we did fine. Burntside and Lonely are a couple of our personal favorites. Good fishing, nice camps with views....
Tom, whatever route that you choose, your group will do fine.
Take your time and let the 12 year old set the pace, you will have fun.
Have a great time.
GeneM