movie title. can you help me?

I watched this movie that was a horror I would say. However it was twisted and funny at the same time. It was about a mother, father, and their teenage daughter, her boyfriend I believe and her younger brother driveing at night down a backroad going somwhere. They kept going and going but kept coming through the same town. along the way, they came across a woman with what appeared to be a baby in a stroller, and I forget, but either the baby was dead, or it was not real. but the movie was really weird and funny. The mother started wigging out and acting like she had alzheimers or somthing. Does anyone recognize the movie and know the name of it???. Everyone pretty much died by the end of the movie. if not all of them.