I did and it actually helped! Ds trained last oct at 2.4, ok till dd born in jan then major regression. Stuck it out till Easter but couldn't face him weeing all over my mums lovely carpets so reluctantly put him back in nappies for a week. Had another go when we got home and he's got it hurrah! I reckon do what makes it easier for you and enjoy your holiday
I should think that the stress and upset and worry about soiling themselves constantly will do far more damage than allowing him to wear a pull up and regroup. Perhaps he's not feeling quite right might be worth getting him checked out.
What about the old fashioned, but very useful, training pants? We have had two types. One is thick terry with a waterproof cover which we tended to use for the boys, especially if we were out of the house and the other are just terry pants over which we put plastic pants in the early days of a child's training or when we were out or in the car. They are not a nappy and can properly be called pants, they keep the worst of a wee in one place, make the child feel that he or she has done something much more than disposable pull-ups and don't cost a fortune - ours will be doing their fifth child in a year or so.