"Aqueles são pequenos."
Translation:Those are small.
There is a slight difference between 'they' and 'those'. 'They' is simply 3rd person plural, which in Portuguese is 'eles'. English uses 'these' and 'those' to create a contrast between things/people that are near the speaker (these) and things/people that are not near the speaker (those). Portuguese does the same thing with 'este/esse/aquele. In Portuguese, 'aquele(s)' is an even stronger distinction than the English 'those'. A good translation for 'aqueles' is 'those over there'.
Actually, in Portuguese the distinction between este/esse/aquele is not about proximity to the speaker (at least directly), but rather about the grammatical person near which the thing referred to is. In more detail, "este" would be "this one near me/us", "esse" would be "this/that one near you" and "aquele" would be "that one over there (away from both speaker and listener)". The same rule can be applied to isto/isso/aquilo, "aqui/aí/ali" and "cá/aí/lá".
Thanks for explaining this better than I did. :-) I forgot the detail about near/not near the speaker. As a native speaker of English, to me it's intuitive, so I don't think about that distinction.