We have booked the night tour of the Colosseum which starts at 7:30pm. But we now realized that restaurants don't reopen until that same time. We have kids ages 8 and 11. Is there anywhere to grab a quick bite to eat, even if it's street food, near the Colosseum area?
Some casual pizzerias are open all afternoon - both sit-down types and pizza by weight. Rick's book lists several in the Monti and "Behind the Colosseum" sections (p. 944-5 and 972-4 in the big Italy book). These include Chicco di Grano, la Boccaccia, and Trattoria Luzzi.
I can't provide specific restaurants like Laura has but as we skip lunch, we often eat unfashionably early in Italy and have not had a problem finding places which are open before the 7:00 hour.
We ate early there in April of this year - around 6pm. We wandered from Colosseum back towards our hotel near Pantheon on foot. There were lots and lots of places to eat.
I remember Take Away sandwiches shops being open at that time.
Try Trattoria Pizzeria Luzzi, about two or three blocks from the colosseum on Via San Giovanni in Laterino 88, very near to the San Clemente Basilica ( which is a really interesting church to visit, built on three layers, Roman ruins, Middle Ages structure and today's church.). Luzzi has its own website and is also on Trip Advisor. Good food, very reasonable prices. We ate a very late lunch there and were in and out fairly quickly. Mixture of tourists and lots of locals eating there.