Answer:
A long narrative story.
Step-by-step explanation:
The word "saga" is defined as "a long detailed account" of some event. originated from the 12th and 13th centuries in Iceland. This word is used to mean any detail that includes a long prose narration of any event.
Likewise, the use of the word in the given sentence best means "a long narrative story". Based on the context of the sentence, we can know that the "saga" of the "summer vacation" will contain "complex details". And by the statement that "you could tell us just a quick, five-minute summary", we can say that the "saga" is a long story.
Thus, the correct answer is the first option.