The evidence at the moment, as I understand it, is that there are genetic factors but also lifestyle triggers. And not every child of a T2 parent gets T2 themselves.
But cutting back on highly processed foods and reducing the amount of sugar in the diet is a good start.
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.