I'd definitely feed any child of mine the same type of normal full fat ,moderate carbohydrate food and a decent amount of protein that I ate while growing up post WW2, and for most of my adult life. I'd also tend to discourage constant snacking particularly of carby, sugary rubbish between meals.
ETA I only ever came across one T1 child - but none with T2 that I was aware of during my teens.