Based on information from Paul, I was able to reach colliseum and Norman's on the Ottawa, by the road.
The road starts on Grants Settlement road here: 45.716051,-76.769564. It's a small unpaved road south of the B&B.
Unfortunately there was a locked gate, but I decided to park the car there and walk. At the end of the road, which is in pretty good contrition, car accessible, there is a shed and a back house that is used by one of the rafting companies. There was a raft with paddles, pfd and helmets, waiting for a group I guess. Then, at low levels, (river was at 0.25), you have to walk quite a bit on rocks. It's not that easy, since those rocks were under water in the spring, they are full of dried aquatic plants.
You can reach Norman's and colliseum
