Meeting with a nutritionist is the biggest thing. Eating sugar free is not helpful to most Type 2's because many things without "sugar" still has a high number of carbohydrates. Your husband will have to learn how many carbohydrates he can handle and still keep his sugar in "goal range", this is something that is pretty unique to each person and has a lot to do with portions. They will also discuss a healthy weight that he needs to maintain.
Disney has a lot of healthy options for eating, but every diabetic is different. I for example can eat full fat ice cream, candy, and chocolate with little impact on my blood sugar, however a piece of bread (even whole wheat), a banana, potatoes, or rice will send my sugar into orbit. I have very good control of my sugar, but I know if
I want a sandwich I need to cut carbs other places and also exercise more that day [Looking at a one hour swim, makes the bread basket look less attractive]. My father on the other hand, is barely affected by bread products, but if he eats fruit (especially apples) his sugar spikes, go figure and we are genetically linked.
So they key for your husband is going to be seeing his nutritionist, probably food label reading and carb counting in the beginning, and most importantly frequent testing. Nothing Disney has is different from the real world.
As far as the Dining Plan goes, it is too much food for most people (not just diabetics) I know I don't eat dessert at every meal at home.
We don't purchase the dining plan, but have been at Disney during
free dining. I never hesitated to ask the server if instead of an entree it would be possible to have a nice dinner salad (A salad without dressing (I don't like dressing) has nearly no carbohydrates, add a little protein, skip the carrots and it is a nearly perfect net zero carb meal for nights I may want some disastrous dessert). They have always been accommodating. For me I also ask them to keep the bread off the table, since it is one of my "bad sugar" foods and also something I would eat all day.
Finally, I ask them if I can substitute some fresh fruit for dessert. I am not saying I won't have a bite of my husband's, or even sometimes order my own; but every night I don't need dessert. [Not sure which dining plan you are on, but the counter service locations can give you either apples or grapes (can't remember which) from the kids meals instead of cake].
This is going to just be a long trial and error for you and your husband. When I was diagnosed as a diabetic, it was immediately after having my thyroid removed due to cancer, I attended a 4 week class at my hospital "diabetic education" with my husband. My husband is not diabetic, but wanted to get an idea of my new challenges, since I was a healthy weight I just needed to learn sugar control. Husband was overweight, with
annoyingly perfect blood sugar numbers, and actually managed to learn enough about nutrition to lose some pounds. Then a few months after the class, I started seeing a nutritionist because I was finding that some of the information that seem appropriate for the "masses" of diabetics did not really apply to me--such as the whole grain bread thing? Meeting with her really helped me to customize a plan that was both healthy and workable in every day life.
What I guess I am saying is this is going to be a life long journey for your family, not just your husband. A trip to disney as a diabetic means, making smart food choices, drinking lots of water, and maybe getting to be a little bad because your doing extra walking. For me it's not really different that being at home, and having dinner at a restaurant. There are always things on a menu that are "bad sugar options" for me, but I just need to make balanced choices.