Learn French: Nous sommes toujours prêts pour eux.

Eux is a stressed pronoun. In French, you must use stressed pronouns after prepositions like pour (for), avec (with), or sans (without). Because of this rule, "for them" is always pour eux, never pour ils.

Does eux refer to a group of men or women?

Eux is the masculine plural stressed pronoun. You use it to talk about a group of men, or a mixed group of men and women. If "them" meant a group of only women, you would use the feminine stressed pronoun instead: pour elles.

Why does prêts have an "s" at the end?

Adjectives in French must match the number and gender of the person or thing they describe. Since nous (we) is plural, the adjective prêt (ready) gets an s added to the end. If "we" was a group made up entirely of women, it would add an "e" and an "s": prêtes.

Why is toujours placed right after sommes?

In French, short and common adverbs like toujours (always) usually go immediately after the conjugated verb. The word order here matches English nicely: "we are always" translates directly to nous sommes toujours.