Cuando lleguen los invitados, ya tendremos preparada la mesa y mi madre habrá dejado envuelto cada regalo.

When the guests arrive, we will already have the table prepared and my mother will have left each gift wrapped.

Breakdown of Cuando lleguen los invitados, ya tendremos preparada la mesa y mi madre habrá dejado envuelto cada regalo.

• tener: to have
• mi: my
• cuando: when
• nosotros: we

Questions & Answers about Cuando lleguen los invitados, ya tendremos preparada la mesa y mi madre habrá dejado envuelto cada regalo.

Why is it cuando lleguen and not cuando llegan?

Because cuando is referring to a future event here: when the guests arrive.

In Spanish, when cuando introduces an event that has not happened yet, you normally use the present subjunctive, not the present indicative. So:

• Cuando lleguen los invitados... = When the guests arrive...
• not Cuando llegan... in this future sense

By contrast, cuando llegan would be used for habitual or repeated actions, like:

• Cuando llegan los invitados, siempre abrimos una botella de vino.
  = When the guests arrive, we always open a bottle of wine.

So in your sentence, lleguen is there because the arrival is still in the future.

Why is it tendremos preparada la mesa instead of just prepararemos la mesa?

These two are related, but they do not mean exactly the same thing.

• Prepararemos la mesa = We will prepare the table
• Tendremos preparada la mesa = We will have the table prepared / ready

The structure tener + object + past participle often means to have something in a certain completed state by a given time.

So tendremos preparada la mesa focuses on the result:

• by the time the guests arrive, the table will already be ready

It is very similar to English we will have the table prepared or more naturally we’ll have the table ready.