|Subject: Re: Rome: St. Peter's to Coliseum?|
Yes it is a very long walk. I would say 3 hours is about right for the Vatican Museum. I rented a recorded guide, but then I was alone. It may very well behoove you to get a guided tour since there are 3 of you. Also keep in mind that the museum, which contains the Sistine Chapel and St. Peters are a fair distance from each other.
There is an express bus close to the Vatican #40 that takes you to Piazza Venezia which is very close to the Colisseum and of course the Forum. Make sure that you buy your bus tickets at a news stand since you can not pay on the bus.
The Metro line for St. Peters does not go to the Colisseum, You would have to transfer at Termini, and I don't think it is worth it given your time frame. Taxis are expensive and not always faster than the bus, they also have a tendency to take the long route.
Fanny in NYC