Golden rule - keep a steady pace rather than pushing it.
I never take any more repair kit than I would for a 25km ride when riding a 100 miler.
Foodwise - it can be difficult to digest food if you are not used to eating when cycling longer distances, so maybe consider breaking the ride into shorter sections and plan to stop for something to eat. Nothing too much, but sufficient enough for fuel.
I never take "sports drinks" as I find it upsets my stomach and just stick to water.
Enjoy it.
(edit - bananas. They are good. I always have one just before setting off, then another after about 20-25 miles. Easy on the stomach too.)