The Matsu valley streams have taken a big hit on the salmon returning over the past few years, last year they closed most of the rivers to salmon fishing due to the poor runs. That isn't saying it will happen again this year, just something to be aware of. You really want to talk to Ard, he fishes all over that area and can give you his best views on fishing. In the meantime, browse around this site it has some interesting data on fish returns and what fish are in the rivers at any particular month of year.
Sport Fish Run Timing, Alaska Department of Fish and Game
We also have several other Alaska members, hopefully they will chime in and offer some advice.
Edit: I sent you a PM!
The Russian River River flows into the Kenai above Soldotna, a very popular area for the wade fisherman, but it is combat fishing to the 10th degree. However, by looking at the AK Fish and Game fish counts you can see when the Sockeye enter the river, more toward the end of June., peaking on the 23rd. Monitor this web site and you will get a good idea of what is happening before you leave for AK. They will also post any fishing closures on this site due to poor salmon runs.