I just stepped up my distance to riding a metric century recently, I'd recommend putting in a couple of 40-50mile rides before the full distance to see how you pace yourself, rather than working that our on the day. Also use those rides to understand where you might have comfort issues. You'll want to have a proper sports drink, like HEED or cytomax and try your granola bar, or if that doesn't work for you a gel. The advantage with powdered drinks is that you can take more with you in a ziploc and make up fresh if you can find water half way into your ride.

Good luck.