Itinerary and a few Questions

We are visiting Rome for six and a half days the last week of June and are trying to get organised, but at the same time leave some time to wander and explore without any set plans.

We have some things pre-booked, and others to book when tickets become available, but there are a few things on our "maybe" list that we have not pre-booked for and are getting conflicting information from Google as to whether pre-booking is necessary or whether we can simply turn up on the day. We don't mind a bit of queuing. We're English - we're experts on queuing already ;)

Our itinerary is below with the items in bold either already booked or will be when the tickets become available to buy from the official sites. Is there anything on our not booked/maybe list at the bottom that you would anticipate being impossible to just turn up for please?

Day 1 - Nothing booked in case we are delayed at the airport but if we aren't we have a free afternoon to start.

Day 2 - St Peter's Dome Climb first thing in the morning - we didn't fancy the idea of climbing up there in the afternoon heat. Vatican Museums in the afternoon.

Question: I see that no phones are allowed in the Sistine Chapel and the Rick Steve's audio tour I would like to listen to would be on my phone. Would that be an issue? Is it just no photos and phones on silent or are they under no circumstances?

Day 3 - Borghese Gallery (providing I can get tickets) in the morning. Afternoon free. Rome by Night Bus Tour in the evening.

Day 4 - Colonna Palace in the morning. Afternoon free. Opera in the evening.

Day 5 - Free day, though if we have not visited the Pantheon by this point that will be on this day.

Day 6 - Pompeii and Herculaneum

Day 7 - Colosseum - Hoping for attic tickets but will get the basic as a fall back if not.

Question: We are planning on either early or late in the day tickets for the Colosseum on the basis of the single entry to the various venues rule. Please correct me if I am wrong, but my understanding of how it works is that if we, for example, went into the Roman Forum as soon as it opened, had tickets for the Colosseum mid morning, and had not seen everything we wanted to in the forum by the time we needed to go to the Colosseum, we would have to miss the rest of the forum as we could not go back in again.

We also have a seven day ticket for the National Roman Museum, though I see one of the four sites is currently closed, that still leaves 3 to visit, two in particular we would like to get to.

In addition we are looking at the following places as our potential/maybe options, depending on what we feel like and whereabouts we end up when exploring during our unplanned time. We are realistic in that we won't be able to cover all of them in the time we have, especially since we would like to cover places like the Spanish Steps and other notable places.

Anyway, it would just be handy to know beforehand if any of these are ones where if we don't pre-book we are going to be completely out of luck.

• The Pantheon. This is one that really gives different advice on pre-booking. Again would be doing the Rick Steve's audio tour.
• Galleria Doria Pamphilj.
• Capuchin Crypt.
• Capitoline Museum.
• Baths of Caracalla.
• Castel Sant'Angelo.
• Leonarda Da Vinci Museum - there appears to be 3? Is one particularly recommended over the others?

Thanking anyone who can help in advance. :)