A few other pieces of advice.
Churches - While most of the churches look drab and in need of cleaning, the interiors are spectacular and range from Byzantine to Baroque decor. We visited about a dozen, some intentional, others by happenstance. We were not disappointed. Churches were free to visit. Some charge to visit their crypt and/or museum. Photos were allowed in most except during mass. If you want to see something fascinatingly creepy check out the church of Santa Maria della Concezione dei Cappuccini on Via Vento. Pay the money to see the museum and crypt. The crypt is decorated with the bones of monks and features a pelvic room among others. No photos were allowed, but the macabre setting remained memorable.
Ruins - The Colosseum was spectacular and took us half a day to visit. The ticket also allowed us to see the Forum and Palatine Hill. Online we read that the ticket was good for three days. When we purchased our tickets, they were good for two. Allow more time to see the Forum and Palatine Hill. The area was vast and awe-inspiring. I could have spent more time wandering about. If you are short on funds, there are other sites that you can see for free. If you go to the the Colosseum on Sunday you'll experience a slightly surreal treat. The main road from the Colosseum to the Il Vittoriano Monument (aka The Wedding Cake) is closed to traffic and families, friends, and lovers stroll along the wide boulevard during the day.
The Vatican - We paid a lot to go on an early morning tour of the Vatican Museums before they opened to the general public. We got to see the Sistine Chapel with about 25 other visitors and could comfortably sit or stand to take in the masterpiece. Based on the subsequent reports, this was a good move. Later on one can be packed in like a sardine. The Vatican Museums were vast and we did not have enough time to cover the other parts. If you go, do not let the tour convince you to exit. Take your time. The museum even sports cafes for lunch. Upon exiting, make sure you take time to make your way to the dome. Pay the extra two euros for the elevator because you will still climb an inordinate amount of curving stairs to the very top. This was the only dome where we could climb to the top (at least from the places we visited); worth seeing Rome from high above.
Food - Because we were a party of four and not two, we stuck to more of the touristy places and dined outside upon checked tablecloths a fair number of times. We only had one abysmal experience (near the Vatican) and we left before we ordered food. Pasta and pizzas were all good. My father loved the fresh tomatoes and I enjoyed the Roman artichokes. We did hit up one organic place on Via Urbana and we had lunch at a garden patio featuring a potato, white bean, and octopus salad (very delicious). One of the checked table cloth places had a waiter that reminded us of Nathan Lane. He took a shine to our family and at the end of the meal plied us with limoncello and amaro free of charge. If you have time check out Campo de'Fiori, the morning food and flower market. They feature all kinds of produce with a few meat and cheese vendors for good measure. A feast for the tummy and the eyes.
I'll leave you with a few photos. If you want more, check out my flickr site.
I hope you enjoyed the brief glimpse. Ciao!