How not to make a meal out of cooking Christmas dinner for the first time

Hell is other people, said Jean-Paul Sartre. The French philosopher was better known for frequenting the cafes of Paris than for his domestic side, so his thoughts on festive cooking are unknown, but hell descended upon my kitchen last Saturday, when I offered to cook Christmas dinner for my parents and my in-laws.
Most families with ‘kids’ my age are in a period of transition, where the new generation are taking over from the original series of parents who’ve done the hard graft for two decades or more.