Just in case you haven't seen it already, fishing info for Yellowstone is
here.Driving around the Park, we have seen most fishing being done in the Firehole River between the Old Faithful area and Madison Junction and again in the Madison River between Madison Junction and the West Entrance. Lots of folks doing fly fishing.
At Canyon, stop at the first parking area on the North Rim Drive and hike down the the brink of the Lower Falls. Spectacular to look over the railing and watch and listen to the roar of the water falling some 300 feet into the mist below. All of the pull offs on both the north and south sides of the canyon are worth a stop. A nice new Visitor Center at Canyon too.
Plan on a full day at the Old Faithful area. Lots of trails/boardwalks there and lots more thermal features that just the Old Faithful geyser. Stop in the Visitor Center to get the estimated times of the predictable geysers to help plan your route. Have lunch in the Old Faithful Inn (less expensive than dinner). Stop at Black Sand Basin and Biscuit Basin while in the area.
You will see Bison all around the Park, but in our experience the largest herd is in the Lamar Valley toward the Northeast Entrance. That's also the only place we have seen Wolves. Wolf, Eagle and Bear sightings are pretty much a matter of being in the right place at the right time, so luck is involved. The Rangers can probably advise on recent sightings. If you see folks on the side of the road with spotting scopes, you will know something is going on. Hopefully you are bringing binoculars, although folks will spotting scopes will often let you look.
You will have no problem filling 5 days with activities in this unique place.
