RE: Allentown PA Christmas Dinner
On Christmas Day, about the only restaurants you'll find serving dinner will be hotel restaurants, Japanese steakhouses, Chinese buffets and Waffle House.
However, the King George Inn usually has a Dickensonian Christmas Eve dinner.
Cab Frye's is a wonderful restaurant but will be closed for Christmas. The holiday menus on the link are for holiday office parties or similar group dinners.
There are a couple of country inns where the owners live in the building and they are sometimes open for Christmas dinner. I'll call around and check for you this weekend because many don't have websites.