Our family always ate out after Mass on Sunday. Many of the people working in restaurants on Sundays are simply not concerned about not working on Sunday. If you have no choice about working, it is not a sin to o so.
I remember two of my children facing that problem as teenagers. One worked in a book store, the other in a hardware store. Both were open on Sunday. The owner of the bookstore was a Conservative Jew, and did not work on the Sabbath or on Jєωιѕн holy days, leaving the sore in the care of an assistant manager. When my son was hired, she asked him if he had any religious restrictions on when he would work. He told her that he could not work on Sundays, Good Friday, or Christmas. The store was closed on Christmas because there were no customers. She had no problem accommodating his desire to be off on Sunday and Good Friday, and said she admired his dedication. The hardware store manager was less happy about it, but he didn't push it either as long as my son was willing to work any other days asked.