I thought that the Vatican Museum tour was excellent. The amount of history and art that is located here is mindboggling, from the frescoes to the statues, virtually every nook and corner (even the floor) is a treasure. The Sistine Chapel is breathtaking, but be forewarned: cameras are not allowed in this part of the Museum (and the ushers enforce this rule strictly).
I would definitely buy reserve tickets in advance, as the line for general admission was literally about 4 blocks long, and I was there during the "slow season" (early March). If you have advance tickets, you can walk right in!
I'd also recommend purchasing the guided tour, our tour guide was very knowledgeable and she pointed out a number of things that I never would have noticed had I try to absorb everything on my own.
One caveat is that small/younger children might lose interest quickly. The tour is about two hours long if I remember right, and the few children in our tour group were pretty bored pretty quickly.




