Hey Amanda!
I think the rationale of doing AK before you get to BC makes perfect sense! Plus it will give you an idea whether you have any desire to fit any extra time at AK into the rest of the trip right at the outset.
As for the autograph books, one year I did homemade ones which turned out quite nice, but they took me forever to complete. I probably would still be making them on every trip, but I stopped because I found the kids didn't tend to treat them the way I would have hoped.

I am obsessive about my books, ect. I don't like bent pages, ect. Watching my son scribble in his, and seeing how they got tossed into toyboxes after the trip made me stop going through the enormous effort. The last 2 trips I have bought ours.
However, if you could be particularly diligent about protecting the books you make, and then immediately stashing them away somewhere safe when you return to preserve them, I think it would make a great keepsake, and would certainly be a lot more special than the store-bought ones.
If I had more time I would probably try them again, especially now that the kids are older. But realistically, I am not sure I will be going down that road again.