Hi Stewman.
I am the parent of a twenty eight year old who was just like that when he was a sprog. He is as bright as a button and we are all autistic in my family which makes life easier as we all 'get' each other.
In fact we used to eat our meals and he had his own food separately.
I used to joke he would eat anything as long as it was chicken nuggets or turkey dinosaurs and smiley potato faces. Everything I cooked for him was twenty minutes at 200C LOLS
You may be encouraged to hear that when we eventually met up again with the family of one of my friends who had had kids who would eat anything - he was by then the adventurous one and they were the ones who had become scarily picky eaters!!!
I would just carry on buying him his preferred foods if it isn't too difficult for you to do that.
The more we tried to get him to try new things the worse he got.
Just focus on your own diet and when you find excellent things (and you will) that are good for your diabetes and also wonderful treats he may come round to your way of eating eventually. In the meantime he'll be okay.
I have a page on Facebook with recipes I've found in my adventures into keto and they are very low carb and in most cases nicer than the high carb versions.
In the meantime there is a thread on this forum called - What Did You Eat Yesterday? and that is a very useful section for food ideas.
My page is at
https://www.facebook.com/MeTacklingDiabetes
Today I am making keto chocolate eclairs with real whipped cream and chocologic chocolate.
They are in the fridge chilling
🙂