Check out Swanson Review. It's targeted for the FM board exam but it's good for the medical student shelf as well. I did about half of the questions and ended up honoring the shelf. I felt that the actual Family shelf questions were much harder than those in Swanson's. I would suggest preparing for the Family shelf as if you were preparing for the Medicine shelf (e.g. PreTest, BluePrints, even MKSAP if you have time). In my opinion, the Family shelf was the hardest of all the 3rd year shelf exams.