Learn Spanish (Latin America): Mi familia va a México pronto.

The verb ir (to go) almost always needs the preposition a (to) when you are talking about a destination. In Spanish, you can't just say va México; you have to connect the verb and the place with a, making it va a México (goes to Mexico).

Since a family has multiple people, why do we use va instead of the plural van?

Even though a family is made up of several people, the word familia itself is a singular noun (one family). Therefore, it takes the singular he/she/it verb form, which is va. You would only use van if you were talking about multiple families (las familias).

The translation says "is going," but doesn't va mean "goes"?

It means both! In Spanish, the simple present tense like va can mean "goes," "is going," or even "does go." Because the sentence includes pronto (soon) to talk about the near future, "is going" sounds the most natural in the English translation.

Why does México have an accent mark over the 'e'?

The accent mark tells you exactly where to put the stress when you say the word. It shows that you should emphasize the first syllable: MÉ-xi-co. Also, remember that in this specific country name, the 'x' makes an 'h' sound in Spanish!