Road Trip: Mountains!

Tomorrow morning, my family and I are embarking on a road trip to the mountains of North Carolina!  For the drive, I will be in the backseat with my two siblings.  I'm super excited to go on vacation, but two things worry me:  I get carsick in the backseat and family vacations/trips always stress me out.  Today, I've been packing and stressing like crazy!  It doesn't help that I've been sick and still seem to be dealing with something.  Sinus junk has been making me sick, and nerves are upsetting my stomach.  How fun!  Don't get me wrong because I am excited for the mountains, spending time with my family, staying at a nice resort, going mining for gold and gems, visiting an amusement park, and more, but the stress is really getting to me.  Any advice?