Since its supported he should be fine on water. I usually carry 2 bottles. 1 water and 1 gatorade. In my saddle bag I carry a flat kit, tire levers, multitool and a spare tube. I usually carry 3 clif bars with me. Ive tried the clif shot blocks. They were good when I ran out of gatorade on long rides.
Carry money and ID and find a bar to get some beer at the end of the ride.
Have fun.