Parker,
I've done that float a number of times.
First, dipnetting is only from the bridge in Kenai down, about 60 miles below where you'll be. If you fish for reds, you will be lining them with the masses. An 8wt with a fast sinktip is perfect for this. You will still need to add weight to get down. Be careful about your use of hooks. There is a gap size restriction up there. The Reds take about ten days from when they enter the river to hit the confluence. The numbers jumped dramatically on the 14th so about the 24th, lining...er, fishing should be red hot.
For the 'bows, I use two rods. I take a spin cast and a 6wt. Sometimes while floating you will be a ways from a spot you would like to hit and so I will grab the spin rod and shoot to that location. Other times you will beach the raft and the fly rod will work great. Either way, you need to be bouncing on the bottom or your not in the game. It is fly only water but that just refers to what is on the end of your line. Some of the bows are mondo sized up there. Don't bother bring 6x to this party.
You will only need two different types of flies at this time of the year. Egg flies and flesh flies. You need both of these in a variety of colors. You can literally find the bows on a color of egg fly, catch a few until you get no more biters, switch colors, and catch a bunch more. Don't leave fish to find fish. Stay until there are no more biters. I would check in at Coopers for the hot colors they are hitting on but have plenty of options.
Most people raft the upper so I wouldn't sweat that. I've never been in a drift boat up there in that stretch.
As far as bears go, you very well may see a couple, possibly even close up. The Brownee's along that stretch can be rogue at times. I would try spreading some pro-cure sardine butter on Sauk's back as a repellent (for you). Seems those bears are really keyed in on fish smell this time of year.
Email with any specifics you need.
Steve