One thing to keep in mind is that food and meals are very high priced in Alaska. One way you might be able to save just a bit is to NOT eat at any of the hotels that you are staying at. It is not as easy finding other places, but I think you will be amazed when you see the price in restaurants up there.
Best way is to make sure that there is a bit more in your budget then you originally were planning on. Just to be on the safe side.