Choosing the right combination of survival gear is always a matter of compromises. If you emphasize one aspect, something else will be less optimal. You haven't said a lot about what sort of boating, flying, and other activities you plan to do in Alaska, so the following discussion will but somewhat generic, but I will give you my thoughts.
I think bush flying is one of the most dangerous things one can do up here. If you are in a plane crash in water, the absolute first priority is to get out of the aircraft
FAST! The average person under stress can only hold their breath about 30 seconds. Even if you crash on land, you still want to get out fast because it might burn. A few seconds could easily be the difference between living and dying. If you don't get out and the plane sinks or burns, nothing else matters.
Boating can also be dangerous in Alaska. The water is very cold. The "1-10-1" rule definatly applies in Alaska. If you go in the water without a PFD, you will die (by drowning) in roughly 10 minutes. With a PFD you will have at least an hour (probably a good deal more) before hypothermia kills you. Exiting the boat is usually not a problem. In fact, in most cases you are better staying with the boat as long as possible.
I would not try to combine my survival vest and my floatation. Put your survival gear in whatever ordinary vest suits you. Buy a good manual inflatable PFD, something like the
Mustang 3085 or similar. You can attach a small strobe to the Mustang under the outer cover where it is out of the way and won't snag if you need to exit in a hurry. When you get on a plane, put a good folding knife and fire kit in your pants pockets. Put the Mustang on. Put the survival vest somewhere handy, but don't wear it. If you crash,
get out fast! Many small bush planes are not that easy to get in and out of even under normal conditions. You don't want anyting that will snag or impede your exit. If the plane burns or sinks, you are alive, and have an excellent chance of surviving long enough to be rescued, even without any gear. If it doesn't burn or sink, you can retreive your gear and survive in style.
For boating, go ahead and wear the survival vest, with the PFD over it. (You don't want to inflate a PFD under a vest!) For hiking or other on land activities, where you don't need floatation, you can just wear the vest.
Those are my views. As always, your choices may differ.
EDIT: I see Jerry and I are thinking along similar lines.
ANOTHER EDIT: Jerry's comments about delaying your flight are spot on. Also, I forgot to mention carrying a PLB in your pocket.