Until other southerners chime in, it sounds like it was more of a nice save by the husband after his initial plan was shot downY'all can be singular or plural. I worked with a woman that met her husband on a beach in Florida. He grew up in Alabama.
She was with two friends and he walks up and asked "Y'all want to go out to dinner with me?"
They looked at him and said "All three of us?"
His response was to point at her and say "not y'all, just y'all"