I know it might look like present tense, but it's really future.
In future tense, imprefective verbs (except "być" – to be) are preceeded by "być" in future form (będę/będziesz/będzie/będziemy/będziecie/będą) and then comes the verb itself, which you can have either as an infinitive or in the past form (it doesn't really matter).
But perfective verbs, on the contrary, behave differently. They conjugate just like imperfective ones in present tense without "być". How do we tell them apart from the perfective verbs in present tense…? Simple, perfective verbs doesn't normally exist in the present tense (there are some word-formation rules that allows you to make imperfective variants of them, but that's another story).
So, in other words, verbs "robią" and "zrobią" look very similar, but the first one is present imperfect, and the second one is future perfect. The perfect verbs are derived from the imperfect ones and should be recognisable by the prefix. There are several prefixes that you will see in a great number of perfect verbs, which should help you quite a bit.
EDIT: Also one imperfective verb might have a few perfective derivants with different prefixes. The English Uncyclopedia article on Polish language, while not "scientifically accurate" (to say mildly) in many areas, sums up just that in a funny way.
It's OK, I guess you are confusing "zrobią" and "robią".
"Oni robią prezentację." = "They are making the presentation."
"Kiedy zrobią prezentację?" = "When will they make the presentation?"
"Zrobili prezentację." = "They made the presentation."
"Robili prezentację." = "They were making the presentation (but they didn't finish)."
But... 'When are they giving the presentation' refers to the future as a planned, organized and definite future event. 'When will they be giving the presentation' is similar but more refers to the act in progress at some time in the future. Furthermore, it's rather odd to make a presentation unless you are referring to planning the presentation. We would rather say 'give or deliver a presentation'.
There is often a lot of overlap between the use of future forms in English, and in practice there's not much difference between "are giving" and "will be giving" here. Future Continuous is used to refer to a future event in a neutral way as much as to refer to something in progress. "The government are introducing/will be introducing new legislation tomorrow".
We try to keep Future Simple (what we have here) and Present Continous in the future meaning separately. True, the meaning may be the same, but as we can easily 'pair' these grammatical constructions between Polish and English, it seems better for the sake of learning.
As for 'make/do'... I think that "zrobią" here should be rather equivalent to "prepare", and not to "give". And therefore yes, I guess that 'make' should be again the default version... Also I went with 'the presentation', this makes more sense to me.