Well.....my first suggestion would be to learn what section of river you are going to be floating.
Boundary Creek is a launch point for the Middle Fork of the Salmon. It won't be open then. You would have to launch on Marsh Creek...and maybe that is what you meant.
There is no 'wood in Boundary' that would affect your trip. The wood in Marsh Creek can be challenging, like all logs that try to fully span the river. My guess is that the flows are going to be under 3 feet at the beginning of May. Easier to limbo under the logs at that flow. By mid May the flows will be in the four to five foot range. This is just enough to cover the logs so you can't see them, but not enough flow to get over them.
You should read this article about a trip gone awry.
The participants on this trip knew what they were getting into and several had tons of experience. My kayaking buddies came along and helped them gather some of their gear. One of them had a close enough scare on Marsh Creek (solid 3+ boater) that he quit kayaking after that trip. Completely. It was not even close to flood stage. Just normal highish spring water.
If you don't encounter any full span logs or new log jams it can be relatively easy. Your casual approach to the danger and true expedition type approach that is necessary for a preseason Marsh Creek and Middle Fork run translates into Don't do it.
A much better idea would be drive a car to the takeout and leave it there. Then drive back to Challis and have Middle Fork Aviation fly you into Indian Creek Airstrip for $425 and enjoy the lower part of the MF with no one else around.
We also had a very significant rain event (up to about 8,500 feet) which caused a lot of area flooding in the valleys around here. I can't imagine that it didn't cause some major damage in the Marsh Creek drainage as well (it's only sixty miles from our valley).
You can call this sour grapes if you like, but I have floated Marsh Creek before looking for a body in log jams on our way down. So if you aren't familiar with the run and extremely competent and experienced I would not recommend being one of the first if not the first one down.