We spent a couple of weeks in the Glacier and Yellowstone areas about two years ago...beautiful and worthwhile, even if we were in the car. I did purchase a can of Bear Spray from the local Walmart to carry when walking around (and it would fit a jersey pocket)...black bears are one thing, but seeing a grizzly with cub unfettered by zoo bars is real life. That said, the only animal I saw get even a little aggressive was a bull bison, and that was in response to humans invading his space. Should be a great trip...envious.