Lens suggestion for Brooks Falls, Alaska.

I am cross-posting this question to the Canon Lens forum.

I am going to Brooks Falls, Alaska this summer to view the bears.  Has anyone ever been there, and can you recommend a good lens to take?

I will be shooting with both a Canon 5DmIII (main camera) and a 7D as a backup body.  I have a 24-105 f/4L and a 100-400 f/4-5.6L.  Would either of these be sufficient, or should I opt for a 500mm f/4L or 600 f/4L?  Would either of these two lenses be too much?

Thanks!

Jim