Lunch in Pittsburgh
Pamela's is a good suggestion, especially since there are a few locations. Though, you didn't mention if you were looking for dinner or an early brunch? More importantly, which part of the city will you be staying in? That will make a big difference since you probably won't want to drive far. If you are near downtown, a great place to go on Sundays is The Grand Concourse (located in Station Square). They have a fabulous brunch and also a good selection of food for the little ones. This place would be my first pick.
Pamela's should work well. Please note they serve breakfast all day Sunday but it's really good. There are several locations throughout the city: Oakland, Shady Side, Mt. Lebanon (or is it in Dormont?), Strip District, I may be missing one . . . I personally like the Strip District on the best, though I haven't been to the Mt. Lebanon one yet.