Rome scheduling advice

While you are near the Forum area - take the elevator to the top of the Vittorio Emanuele II Monument. ( Jokingly referred to as the Wedding Cake)
There are views 360 degrees all of Rome. You can spend a lot of time up there taking photos and it helps you to see where various things are located in Rome.
(The Vatican, Pantheon, the river, etc.)
It is located almost across the street from the Forum/Colosseum/Palatine Hill area.

I assume that Saturday is the more crowded day, so do you have any
advice on which day we should do the Colosseum vs the Vatican?

I don't think it matters, really. These are Rome's top 2 attractions, and both will be very busy.

Also, I am trying to book tickets to the Vatican Museums ahead of
time, but am unsure of the time slot. Any recommendations on if it is
better to try to do St. Peter's and climb the Dome early when it
opens, and then book a ticket for the Vatican museum a few hours
later, or book tickets for the Vatican Museum when it opens at 9 am
and then go over to St. Peter's whenever we are finished?

What I'd do? Book a morning, 3-hour combo tour of the Vatican Museums + Basilica. That tour allows direct entry into the basilica via a back passage from the Sistine so you don't have to make the long walk between the two and stand in another security-check line: very efficient. As the museums are vast - although the tour will steer you to just some of the highlights - you may appreciate saving those extra steps! When the tour is over, you're allowed to spend as much time in the church as you wish to. At the point, you can decide if you have the energy left to do the dome. :O)

And I will not swear to this as any day could be different but I read that the line for the dome can be shorter around first thing in the A.M. and at lunch time. If your 3-hour tour ends around lunchtime, that could be an advantage. If you want to stay with just a tour of the museums, then yes, I'd be at the basilica a little before the opening hour, do the dome/church, have a rest-up, and book a later tour.

I would book a Friday night visit to the Vatican museums. This will give you more visiting time for other sites around the city. The night tours are not as crowded as the day time tours.

https://biglietteriamusei.vatican.va/musei/tickets/do?action=booking&codiceLivelloVisita=17&step=1

You can visit the basilica and climb the dome in morning and spend the afternoon at other sites.

I would visit the colosseum area on Saturday because a lot of people visit the Vatican museums on Saturday. Don't get me wrong, the colosseum will still be crowded but not nearly as crowded as the Vatican museums.

Donna

I like to book tours early in the morning, that way I can spend the rest of my day without time constraints. But given that you arrive Thursday, I would book afternoon on Friday in case you sleep late Friday morning.

For the Coliseum, take the underground tour.

I would book a Friday night visit to the Vatican museums. This will
give you more visiting time for other sites around the city. The night
tours are not as crowded as the day time tours.

Great idea. Yes, that would definitely free up time for additional sightseeing!

Vatican Museums closed on Sundays except for free (really crowded) day last Sunday of the month. Friday nights are great!

Thank you all for the suggestions. If we did decide to do the Vatican museum on Friday evening, how inconvenient would it be to do St. Peter's and the dome in the morning and then come back to the Vatican in the evening? We will be using public transportation. Or, I guess we could do other sightseeing in the morning and do St. Peters late afternoon and the Vatican museum in the evening.

Alternatively, if we decide to do all of Vatican City in one shot, and we go to St. Peter's right when it opens, about how many hours later do you think would be appropriate to schedule our museum entrance? I saw in the Rick Steves guide book that he says about an hour for touring St. Peter's and an hour for the dome climb

St. Peter's (which was featured on CBS Sunday Morning yesterday) is fabulous but can be sensory overload, as is the paved road to the Sistine Chapel. But for St. Peter's, once you get in there (and I'm not talking about climbing the Basilica, just on the ground floor), I would say 1 hour gets you the Cliff Notes version, 2 hours seems about right, and take 3 hours if you're really into it. It's that good.

Thank you all very much! I was just trying to book the Vatican ahead of time since I keep hearing how crowded it can be at certain times. We are looking forward to the trip :)