At current flows, you may be hard pressed to even notice anything at the Zuni plant, other than the chlorine smell from the water treatment plant on the other side of the river. The stretch between Reynolds landing and Union is pretty flat/slow. Between Union and Oxford there are a bunch of chutes. Keep your boat between the cairns and you shouldn't have too much of an issue unless you get sideways..
afaic, you can float from c-470 to at least the 85/25 merge without much issue in a raft. The longest drop is near Florida on river left. It has an easy portage but I've never bothered. It's worth running even with the kids in the boat.