Animal crackers and fig newtons make good snacks too. Drink, drink, drink, eat, eat, eat, drink, drink, drink, ...etc.
If you have a fold-up tire, or at least a tire patch, it's a good idea. (You didn't say if it is a supported ride, but if so leave all un-necessary gear in the SAG wagon.)
I found it helpful to concentrate on my cadence, if you have cadence on your cyclometer. Keeping a steady spin is better than hammering, and conserves your energy.
If the sun is out, wear sunscreen, it makes a big difference.
Have fun, go at your own pace.