Can you apologize for someone else? That’s a pretty hollow apology.
It reminds me of when Pat Morita was hired as a stand up comic for a Pearl Harbor reunion. He started off by say, “We are really sorry for messing up your harbor.” It was hilarious because he had nothing to do with it. He spent the war in a Shriner’s Hospital as a child and then a Japanese relocation camp. This man apologizing for anything was ludicrous just as Dahl’s children apologizing for their father.
So basically it would be along the lines of Bill Maher's kids apologizing for him making "anti-religious comments" years after he's dead.