"Amici miei" goes with other films to write the history of the Italian Comedy, or better to say, "la commedia all'italiana" (Comedy the Italian way), which reached its peak in the 1960-70's and turned out to be so different from the comedy genre I happen to know in other countries.
Sour? Oh yes, absolutely sour. In "commedia all'italiana" films, you are typically made to heartily laugh through the film, although the situation may be grotesque and tragic, and usually made of razor sharp social satire. The characters are rather "types", masks embodying (social) vices. They can be embarrassing disagreeable people in which you usually recognise your neighbour. But they cannot be yourself, of course.
Watching this film then, you may be surprised to be shown hypocrisy, compromises, inane wedding lives. These four family fathers enjoy going wild by making pranks to helpless people. They are selfish rogues who never take anything seriously and make a strange contrast with their children, 30-year-old very serious and reliable children. A situation "blinking" to the 1968 disorders and the social commitment of young people of the time, contrasting with the bourgeois way of life of elder people.
Besides, I don't think it is TOTALLY extravagant to think that "Amici miei" is quoting Giovanni Boccaccio's "Decameron". In many of the short stories of this 13th century collection, we see that Florentine people had a taste for pranks since then...
