Starting period sometime bput now and leaving for a beach trip in 3 days?

Im going to jamaica with my family on the 30th. im 15 and share a rooom with my older brother and sister being on my period wont work... we scuba dive, zip line, climb the waterfall, stay on the beach, all day we never are in our rooms so i cant carry around tampons my parents dont believe in them anyways and its an awkward situation due to a situation that happened a few yrs ago.. anyways last month i was off on the 29th so i figured i was ok but i havent started yet and im freaking out this vacation is over $8000 and i cant be acting all awkward and i'll be miserable. What can i do to prevent my period or make it start faster?