Sightseeing in Hong Kong by MTR or Hire a VAN ?

We are 9 adults. Can you suggest for us that is it cheaper if we go sightseeing around HK around 3 days (Ngong PIng, The Peak, Repulsa Bay, night market, avenue of stars, golden bauhina and victoria park) by MTR/Bus or Hire a VAN? Which one is costly? Thank you