Carbo loading like pasta and rice is a very good plan before the ride

My sons, one of whom is competing in the nationals this year, suggest things like sandwiches for you to give him at his "feed-stations"
They also cite the Tour riders as having thjings like custard in buns as they ride.
If he is stopping to eat, sushi or chips might be ok, but if he is not stopping for anything other than toileting, then you want easily eaten/chewed, non-crumbly foods for him that deliver carbs and protein.
How many energy-type bars is he willing to attack in one day

Chocolate milk, or even better - chocolate-flavoured recovery drink made in milk is def necessary when he finishes

A can of creamed rice also goes down well after a hard/long ride - easy to eat and digest

Good luck

Can you post what you settle on and actually use that works for him?