DH and I are both Type 2. I am diet and exercise controlled with Metforman and Jardiance. DH is in insulin and does wear the freestyle Libre to monitor his sugars. It really is great for him, and since he loves anything technical he is in heaven. The best for him is the charts and graphs he can see of his levels over time.
when at WDW, we are both likely to have lows, and they can come on very suddenly. We also pack nuts, cheese sticks and granola. We tend to stay somewhere with a kitchen and start our days with high protein - like an egg scramble with ham peppers and onions. We have discovered that is DH has any carbs with breakfast, he spikes high, if he has protein, and waits an hour or two before any carbs, he is good. It really is finding what works for your body, and learning to listen to what your body is telling you. We also stop and have some small snack every 2 to 3 hours, but some of that might be DD getting hangry. It is especially true when it is hot and humid. I second (or third) the part about staying hydrated.
The walking at WDW is a great help in controlling your sugars, but we have found if we don’t build up to it and train ourselves for a few months before by walking 2 miles 4-5 days a week, we are more likely to have issues with our diabetes while on vacation. I would highly suggest that he start making it part of his routine now and see how it effects his sugars. We find big changes to our usual routine can cause big changes to our bodies, so preparing for them really help.
we are also fans of the Frio bags for carrying his insulin. Especially when it is hot out. They work well on the plane as well, but the monitor (Freestyle) and meds can slow down security if you are not prepared. And I agree with those who mentioned pushing your doctor for more help. There are diabetes classes you can take, and a nutritionist can be really helpful. We were lucky to find a practice that specializes in Diabetes and DH goes in quarterly to touch base with his doctor (I am on the yearly plan since I am more controlled).It works for DH as it helps him be more accountable and controlled. It is really important to find what works for his body and what changes he is willing to make in his life style. Believe it or not, DH still manages to eat chocolate on a regular basis, but he has to walk more and control other things to make it work.
Good Luck with your planning.