A.H.
Hi P.,
I am not sure what the docs will say about his flat feet but I can sympathize. I have very flat feet myself and like your son hate to wear shoes. I can remember going barefoot the majority of my childhood. I find that now in my adulthood that my legs, back and feet get sore after running around shoesless all day. So, maybe try to get him used to shoes slowly.
I can say that from everything I have read New Balance are great shoes for flat feet. They are all I wear because other athletic shoes hurt my feet after a while.
My mother took me to the doctor too as I began to walk thinking soemthing was wrong with my legs. My feet are so flat that my ankles touch and turn it when I stand. He said not to worry that it was only flat feet. I never wore corrective shoes or anything. With the exception of a little fatigue I have no trouble with my feet. I just make hilariously complete foot prints in the sand! :) I hope this helps a little.