I believe I do have a timeline of events that you might find elucidative.
Upon arriving at the restaurant, Jerry realises that it is a posher venue than they were expecting. He reluctantly enforces “Gale Force 5 table manners” on the children.
As compensation, Jerry promises that they will keep the meal to a short two courses and declares open season on the pudding menu. Since Deborah doesn’t like pudding, she is offered the option to have a starter for pudding instead.
Jerry counts them all down to the start of the enforcement of manners. During the five second countdown, the family make wild and rude noises. They stop immediately when he reaches zero and all commence best behaviour.
Deborah wants a story about ghosts, while Myra wants a story about gardens. Uncle Newt compromises by telling them a story about a haunted garden.
Jerry becomes unexpectedly upset when he realises that they have deflated his lilo. In his shock, he shouts: “What have you done? Oh, you cockers!”
He quickly regains his composure and apologises to them all. He explains that he was keeping the lilo blown up because his wife, Hilla, had been the one who inflated it before she died.
He consoles himself and the others with hugs and his refrain of “half a glass”.
He apologises again for swearing at them. However, they are able to reassure him that his lingering aphasia has actually saved him from doing so. They comfort him by joking that “cockers” was at worst akin to “spaniels”, and agreeing that they had indeed behaved like “complete spaniels”.
Before she realises what she has done, Jerry retrieves and blows a kazoo to initiate a family ritual. Hilla tries to change her meal choice to omelette, but the children are already rushing into the room and it is too late.
Hilla, still reading her book, doesn’t join in the chanting in her role as The Flipster. Benji begins to protest, but Jerry (still in character) defends The Flipster’s right to silence.
Although she doesn’t join the chanting this time, Hilla does not want her lines removed from the ritual. She likes it sometimes.
She also gets a small plastic cowboy from the cracker, which she gives to her grandson, Benji. Benji is warned not to snatch by his mother, Hilla, who reminds him that “Level 3” behaviour is expected.
Deborah chooses to pull her cracker with her grandfather, Walter. Vanessa indicates to Walter that his cracker is on his side plate. Deborah wins, but questions if she has to rip up her hat. She asks if that tradition comes from them being a bit Jewish.
Hilla tells her that lighting the candles is because they are a bit Jewish, but that the hat ripping comes from the Wilkinson side. It transpires that the tradition dates back at least as far as Uncle Newt’s childhood.