First of all I wanted to say that I am sorry to hear about your little guy getting diagnosed. It always breaks my heart to hear of another child getting diagnosed. Brings me back to the day my son was diagnosed except he was 4
Having a picky eater is the worst...picky eater and diabetes dont go good together as you have already figured out.
I found my son went into some sort of mode after he got diagnosed...he used to eat anything and everything..but when put on a eating schedule..it really just killed his appetite. Unfortuneatly you are at his mercy. ( Sorry to say)
If he is on some form of long acting...he has to eat at certain times..and if he does not feel like eating.. well this is where we are..SOL.
What we did was talked to dietition...and dropped off on his carbs ( scary I know because you want them to have proper nutrition ).. but it did not take long for my son to figure out that he was hungry again. We are now at a reasonable point..but will be going on pump in fall to give freedom back in this dept.
Blah Blah Blahing along.. I know how you feel. It is a really tough spot to be in as a parent...but for a little while he may just rule in the food dept for a little while