I think the answer is another one of those “it depends...”
I walk a lot (e.g. I averaged over 10 miles a day when I was on holiday) and it makes no difference to my BG.
But if you walk less, it may have an impact ... but it depends how much you are used to walking, how much you eat whilst you are there, how much you stop and start, how fast you walk, what the weather is like, ...
I don’t know about medical letters for Disney (I cannot think why you would) but I have been told you may be able to jump the queue on roller coaster rides if you have a pump.