Sounds like you looked at a chart to know what will be in the river, which tells me he'll be there in June. The best thing to do is monitor the ADFW website and see how the counts are coming for the river. When it gets near their escapement goals, they will open it for bait. The kings up there love good eggs drifted through the big, slow holes. If he is going down in a drift boat and they open it for bait, he will be able to use it once he is below the cabins. Its just a few miles down river from nine mile bridge. Using a drift boat gets you away from some of the goofs that are in the low river below the wier. Don't get me wrong, there are some good folks that fish this area as well, but solitude will not be your friend down there. If it is closed for bait, then Vibrax in size 5 or spin-n-glows are the go to lures. For fly rodding, try the standard king flys (fat freddie, etc.).
The sockeye are pretty much all lined on this river. If he has an 8wt fly rod with a sink tip, that is a deadly combo. The confluence of the old situk and the current stem is a great holding area, accessible only by boat. There will also be a bunch in the lower river below the wier. They come in with each tide so if it is sparse when he is there, just wait for the next high and there will be fish. There is a couple of real good holding areas just below the wier, and a few more spread out down to the parking lot (~ 1 mile).
This is a fun little stream to fish. It is gin clear and you are usually site fishing. There is plenty of LARGE brownies in the area and you certainly need to be very careful. Over the years there has been plenty of bad encounters with them. There is also a decent amount of uptight moose to watch out for. If he is walking in from the lower parking lot towards the wier, the indians now charge for you to walk on land, but walking in the river is free. You can do it during low tides but when the tide is all the way in, it is to deep to walk out so you'll need to time it or use one of the guys that run folks up and back.
Good luck, I've always enjoyed it up there.