Yes, George and Cindy went back to work! They went back to work after smelling that car and knowing it sure smelled just like a dead body does. The smell was coming from their daughter's abandoned car. They went back to work knowing it was the smell of death in that car picked up from the tow yard. They went to work even though they had not seen or talked to Caylee in 31 days, and the car smelled like death. It was a super human denial they had going.
Lee tries laughing at the absurdity of the situation when he has to convey what he, himself, thinks is a bizarre-can't-be-true situation. Tracy did a lot of laughing in her interview, and we know she didn't think it was really funny, but absurd, outrageous stuff. Maybe some people laugh when faced with something bizarre and outrageous to them. Maybe they laugh to convey what even they feel is bizarre.
Or Lee could be kinda dense about appropiate behavior in general. None of the Anthonys have shown appropiate behavior now that I think of it. They would gloss over Caylee's death if they could with a tap dance and a song trying to cover up and rewrite history.