Learn Italian: Vado in vacanza con la famiglia. - I go on vacation with the family.

Andare (to go) is a highly irregular verb. For the "I" form, it changes its root completely to become vado. You cannot use regular endings here — you just have to memorize these special irregular forms!

Why does the sentence use in vacanza instead of a word for "on"?

Prepositions in Italian often do not match up exactly with English. While we say "on vacation" in English, the set phrase in Italian is always in vacanza. You will see in used for many states and destinations, so it is best to learn this as a fixed expression.

Why does the Italian just say con la famiglia instead of translating "with my family"?

Italians often leave out possessive words when the context makes it obvious. Since you are the one going on vacation, la famiglia naturally implies it is your own family. You could also say con la mia famiglia, but it is not required here.

Why is the pronoun io missing from the beginning of the sentence?

In Italian, the verb form itself tells you who is doing the action. Since vado can only ever mean "I go", the word io is usually dropped unless you really want to emphasize that you are going, as opposed to someone else.