I would say that going on holiday early the next morning is not the best indication of him choosing to be dry, as chances are he will get up earlier and have been asleep for less time. Is the wetting pattern similar on holiday, or when sleeping anywhere else, because if he is dry and the only time he's wet is at home, I'd be looking a bit more closely at his routine and habits. I am also wondering if the wetting occurs just before he wakes.
What happens in the morning, does he have to change the bedding himself? Because if you do it for him there is no incentive really to stay dry, because someone always cleans up for him. I think at nearly 7 he is quite capable of removing the wet bedding and pyjamas and putting them in the laundry. He can also re-make the bed for himself, which concentrates the mind wonderfully when he could be doing something else with the time. If it really is laziness I think he will soon stop making work for himself, as he realises that actions have consequences.
Another thing is not necessarily quantity of liquid, but the type of drinks he has. Fizzy drinks, even fizzy water can cause wetting, and certainly cola and hot chocolate (contain caffeine) can as well; also blackcurrant cordial, and in some individuals, milk. Enuresis clinics often advise fizzy drinks not later than lunchtime, and no milk after teatime, so no warm milk at bedtime. It seems that these drinks can cause bladder irritability in some DC. If thirsty, plain water after tea. No well hydrated child should need drinks during the night unless the weather is extremely hot. Obviously, on hot nights the child sweats, so will not have such a full bladder.
Something that is often overlooked is getting the child to go to the loo before they go to sleep, not just when they get into bed. In older children, the gap could be an hour or more, especially if they read in bed. This extra wee before sleep could make the difference between a wet or dry bed next morning.
You could seek advice from the GP when he is 7 if you have tried all the above and he is still wetting.