Need help dealing with potential step family?

My parents have been divorced for 2 years and I am 19 years old. My dad now has a girlfriend who has two sons who drive me to wits end. They are 13 and 15 years old. They have no respect for my father, who I look up to, and none toward me where im up to 6 years their senior. I works hard at both my job and school and now I finally get a vacation and im stuck with them! They are driving me insane and I cannot get a much needed break. I tell them to cut it out but then my father growls at me to be polite! How do I get through my vacation without wringing their necks and getting the relaxation I need?