Towing a heavy travel trailer?

My family has a trip planned that is 1 1/2 hours away (flat roads). Our truck was recently in an accident and wont be available to pull our camper which weighs 8100 #'s. My in-laws have offered us to use there truck, which is a f150 2005. They think it is rated to pull around 6500#'s. It makes me nervous that we could hurt their truck or worse yet cause an accident. My husband and father in law think it would be ok, since it is a short trip and only once. What do you think?