There's a ton of great support from other parents of kids with diabetes in this thread, but I don't see any kids with D talking about their PARENTS! So I'll do it :)
I'm not a kid any more, but I WAS a kid with diabetes, so I have that perspective on the dreaded "vacation with/as a diabetic kid" experience. Indeed, vacations are a total minefield for a diabetic, and especially if you're young and don't have a lot of coping strategies in place yet. I remember very well being really excited, along with my parents and siblings, to go on a trip, only to realize over and over again that the exact stuff we were all looking forward to (fun new activities, sleeping late, special food...) was all going to be problematic for me and cause me to spend much of the vacation feeling pretty bad. It can feel like a total bait-n-switch as a kid, and the height of unfairness.
Here are a few of the things my family did to deal with it:
1. make healthy foods and activities be the fun, special stuff. No one gets a 32oz. coke for a treat because it's bad for everyone, but everyone can have a scoop of ice cream. No one gets to lie on the sofa all day because everyone is going for a bike ride together.
2. my folks let me see that controlling my sugar could be frustrating and difficult for them, too, but that they were always up for the challenge, hopeful and determined to keep at it. No one gave the slightest hint that they thought it was impossible or wanted to give up. I think that's important because it translated directly into my own attitude toward my blood sugar control, and I think it's a pretty good one.
3. I was allowed to get angry and spit a little fire, but no one else was. This is a selfish one, but I really appreciate that when I was growing up I never had to feel like my diabetes was messing up anyone else' vacation (or life, for that matter). If my folks had gotten really upset about it I would have wanted to hide it from them to spare them those feelings, which wouldn't have been good for any of us. At the same time, if I hadn't been allowed to shout about it once in a while I would have exploded.
4. EVERYONE in the family was on board with whatever was good for me, with no argument. This is not to say that if my sugar was too high to eat then no one ate, but that I was accommodated as much as possible with no hint of grumbling from anyone (including my grumbly teenage sibs).
5. when I was young enough to be sent to bed before everyone else they would all wait til I was asleep to break out the dessert. When I got a little older I think they switched to healthier desserts for everyone.
I don't know if any of that is helpful, but I hope so. Strategies are crucial.
Good luck, Natalie!