Rob,
I am a scout leader who has taken crews on numerous wilderness canoe trips. I have never been to the adirondacks for a canoe trip though. Group size is problematic, maximum of nine. Not only can you not stay on the same site, you also can not travel together. Depending on how many leaders you have, splitting into two groups can be a trip buster since you need at least two leaders per group.
Another reason is that from my location the Dacks are not much closer than Algonquin Park in Ontario, or LaVerendrye in Quebec. Algonquin, in my opinion, is the premier place to go for relatively inexperienced canoeing groups who are looking for scenery, wilderness feel, and wildlife (paddling up to a moose is an awesome experience). You won't see near as many people as in the Dacks, and you will see no motor boats once you get interior. They have group size limits of nine per site, but you can travel together and book multiple sites on the same lake. We typically have the adults on one site, and the scouts on another. This is with older, more experienced scouts. Of course, we are also close enough for easy travel to dinner which the scouts prepare.
The last reason, is that if I am in the Dacks, I can't seem to avoid getting above treeline. But, that is my problem. It might also be a problem for getting a lot of response on this site. I recommend you also ask your question at
www.myccr.com , a discussion forum for wilderness canoers. It is focused on Canada, but there are quite a few yanks who are active members. Be sure to include where your home is and and how far you want to travel from home.
If you decide Algonquin can fit into your itinerary I can give you all sorts of route suggestions, canoe rental contacts, and places to stay before and after you leave the park. Here is a link to an older online version of the canoe
routes map for Algonquin just to tease you.
http://www-2.cs.cmu.edu/~crpalmer/algonquin/alg2.pdf
Tony