The hot sun will reduce his blood sugars so keep an eye on them and test regularly, if it's hot, the odd ice lolly will be good for him to bring his sugars up slightly.
I'd tend to aim for higher bloods during the day and more normal at nights, although a lot will depend on his activity during the day and his bedtime routine in the evening.
To sum it up,
keep a closer eye on his levels, don't lose track of time ( for meals and snacks ) , give him a little extra sweet ( if he's in the sun and running about or swimming ), make sure you've insurance and lastly take a camera take lots of pictures and have a great time