Remember, the weight you gain when you 'break your diet' is mostly not fat; it's 'fluid' and glycogen. It's the same stuff that peeled off very quickly when you started dieting. It's 'easy come, easy go' weight. So long as you don't get disheartened and resume unhealthy (over) eating habits on your return, you will not have gained more than a pound or two of actual fat on your holiday.
If you are really strong-willed, I'd suggest you do not weigh yourself until about ten days after your return, by which time you should be eating sensibly again., and should have shed most of the temporary holiday gain.
This is much easier said than done...