I'm trying to figure out the name of a movie by the plot?

I saw this movie a few years ago and I can't remember the name. It's driving me crazy/: It's about a family, Mom(off her rocker), Dad, adult daughter(who's secretly pregnant), boyfriend & teenage son(pot smoking, ipod listening). They are on a road trip during the holidays, headed to visit family. The dad takes a "shortcut" which leads them down a deserted road which seemingly never ends and turns into a nightmare. They encounter a strange woman with a bundled baby, that turns out to be DEAD! Then they all start dying off one by one in horribly, yet funny ways, which include the dad accidentally shooting the mom in the head. Help!!! Does anyone know the name of this movie??? I thought it was Detour, but apparently that's another lost on a dark road movie;)