Hopefully he'll take some classes and have sessions with a nutritionist/dietician with expertise. Also, hopefully he'll see an endocrinologist rather than GP; GPs *can* be knowledgeable, but an endo is a specialist and will probably know more. (if we hadn't self-referred to an endo, if we had listened to the "you're fat, it's type 2, what do you need an endocrinologist for" GP, it would have been much much longer before we found DH's pituitary tumor)
While generalities are good, we have found that what works for one person doesn't *always* work for another. My MIL seems to follow a good diet, but she sits up in the 150s routinely, even while taking metformin. DH now has NO signs and symptoms of diabetes and his endo doesn't consider him to HAVE it anymore, and he took metformin for a week (the side effects were just too much and too embarrassing for him, and his blood sugar was already going down despite everyone, including the pharmacist and endo, telling him that metformin doesn't work that fast so it wasn't the metformin, so he dropped it and stuck with diet and exercise), with just dietary changes and moving more. Two people, two different ways of doing things. MIL thinks her diet is better than DH's simply because he's bigger than her, but in terms of blood sugar that hasn't proven to be true.
With DH, cinnamon is like a magic bullet. Discovered that by accident early on, and later found out that everyone knows about it already, LOL. For the first year I was putting cinnamon in everything I made.
By June, assuming this is a new diagnosis to him (from your wording I didn't know if YOU are just finding out about it, or if it's new to him, too), everything will be settling down. He might have the "afraid of food" response, and that should be settling down, too. He'll have started to learn what works *for him*. And if he feels brave enough to do Disney, then good for him.
Another part of discovering what works for him...watching what KINDS of sugars he eats. For DH, he can eat something truly homemade, from scratch, even chocolate cake, and it would bring his readings up *a bit*. If he had a soda with HFCS, even though there were fewer carbs than the cake? Forget about it. He was shooting sky high, flipping out, and crashing HARD. His flipping out while sky high involved starting random, nasty, arguments with me. One fabulous moment when he decided to have dessert and a Bailey's (when he barely drinks) involved me locking myself in the bathroom while on vacation at Universal because he would not stop picking at me. I did not want to engage, and let him know that he needed to eat some protein and check his blood sugar while zipping his mouth shut, and I locked the door and took a bath. When I came out he confessed that his sugars were scary-high, he had eaten a protein bar and had a bunch of water, and he wasn't going to say more. Whew.
For him, a Dole Whip would have been BAD. in fact, it was a Dole Whip that helped give me a clue (long before he actually had a high reading), because he and DS had them at
Disneyland. DS went manic, running aorund in circles and not listening while being violent with me, and when I looked to DH for help, he had pretty much passed out on a bench. AWESOME. Dole Whips have corn syrup solids in them, and that moment was when I realized DS couldn't have those, either (along with corn syrup and HFCS), and DH shouldn't, either. After 5 years of avoiding that stuff, DS had some, and now his reaction is more like DH's. Fabulous. Something in their genetics!
So that goes along with finding out what works for HIS body. It's NOT one size fits all.