Prince Harry turned into a suburban dad struggling to get a bunch of hyper kids to listen to him -- but at least it was just for a day ... and for charity.

Harry was coaching a handball match for toddlers at an East London charity event. Most of the kids didn't seem to pay much attention to the Prince -- in other words ... he's ready to coach youth soccer in America.

The charity's called Fit and Fed and is similar to Michelle Obama's Let's Move program, promoting nutrition and an active lifestyle for kids.

Harry was pretty patient with these tots though -- maybe a career change?

Nah, he's a freakin' Prince!!