I'm doubtful of the decision not to vaccinate, though they are not unique in this respect. If you read magazines such as Green Parent or Juno, which deal with alternative methods of child-rearing, the anti-vaccination movement is quite strongly represented. It is motivated by concerns over the safety and effectiveness of vaccination, and has presumably been influenced by the now-discredited (in most people's minds) link between vaccination and autism. Well-meant, certainly, but I think they are wrong.
As for the rest...It's their choice and I can't see that the children are being harmed. They're not the only family in the world who choose the unschooling way, and a child with two loving, easy-going parents are surely better off than a great many kids who are undergoing traditional schooling but don't have close and loving parental relationships.
My DD has recently chosen to home educate her little girls and I am helping her, and I support her decision to do what she thinks is best for her children. It wasn't made lightly or easily. We are taking a semi-structured approach but trying to allow plenty of free play and expression as well as literacy, maths, etc. All home schoolers are different, and who is to say how this couple's kids will turn out? It may be that they will blossom through this sort of childhood.