Go along and have a word with your doctor. He/she can prescribe a progesterone pill that is designed specifically for delaying periods. I have used this several times in the past when I have had important trips to go on.
You start the tablets 3 or 4 days before your period is due if I remember correctly. You take them three times a day. As soon as you are ready for your period to start you stop them. Then a day or two later your period starts. Please note however they don't have any contraceptive effect.
Hope you have a good trip