I had our four days in Rome mapped out and then my son mentioned he really wanted to see the Borghese Gallery and some of the sculptures there so I'm figuring out how to fit it in knowing I need to figure it out now or not get a reservation. This is what I have so far
Sunday arrival--pretty much strolling down Via Del Corso including Spanish Steps, Trevi Fountain, Pantheon, Emanuele monument and elevator....Dinner in Trastevere
Monday--Vatican Tour 830-1130am, lunch break, Scavi Tour 145pm
Tuesday--day trip to Pompei
Wednesday--Ancient Rome with a 820pm night tour of the Colosseum Underground---my thoughts are to schedule the Borghese for this morning and since we will be at the Colosseum late plan to be there by 2-3pm to tour the Forum, Palatine Hill and Colosseum. I know I have to use transit to do this is it feasible or should I try to put it on day one or two?
Monday is already busy and another museum will exhaust you and overwhelm. Tuesday is out as it is a long long day, so Wednesday it is. Morning is a good idea. Try for the 9:00 AM entry, then chill out and rest. The Forum, et. al., will be hot in the afternoon. As the Forum et.al;. are open until 19:15, why not go later, when there might be some shadows, say about 17:00? Spend about 2 hours on the Palatine Hill and Forum then take a little break before your night tour at 20:20.
The Borghese is fabulous by the way. Rent the audio guide for a better experience.
Would you consider going to Ostia instead of Pompeii on Tuesday? If you did that, you might be able to fit in the Borghese later that day (the museum is open till 19:00 - at least, it is now; I don't know what time of year you're planning to go). Even if you don't go to the Borghese, Ostia has interesting ruins and it's easy to get there from Rome.
I know some people like to suggest that Ostia and Pompeii are comparable but they really are not other than two old, abandon cities - one slightly buried in mud and the other completely buried in ash. If you didn't have time for Pompeii then I might suggest an afternoon in Ostia but they are not the same.