If you decide to go the backpack route, just be sure to have all the compartments closed securely. My boss was traveling using a backpack, and someone stole her wallet from one of the little pockets while she was wearing the backpack. My boss was notorious for not closing those the pockets, so it was probably like an invitation to a thief.
Also, you know the times you should be leaving and arriving, but in my experience it's unusual to hit those times. So, whatever you carry, bring some things to pass the time - crossword puzzles, snack bars, etc. And have fun!