As of now, I have in our itinerary to eat lunch both days in our travels. For lunch on Saturday, there is about 2 hours allocated at the Gallery at Market East. Of course in that area there's also the Reading Terminal Market and countless places along Market Street and side streets, if anything suits you better. Should there be spare time, there's always the SEPTA museum/store if it's still open Saturdays. For lunch on Sunday, one hour at 30th Street Station should be enough.
Which brings up the question of our usual Saturday dinner for the winter RailFests. I don't think too many of us are in the mood for an expensive sit-down steak dinner. There are a few diner-type places in Center City, similar to the Skylight Diner in New York from last winter. However considering that we presently have only 7 people on Saturday, and 3 of them can go home and eat dinner, we don't necessarily need to have a formal group meal.