In the spoken language the present tense is often used to indicate future actions.
To be grammatically correct you only have to use the present tense for future actions if you have a relation to the present in the sentence. In this phrase you have the word domani (tomorrow) which is only "tomorrow" seen from the present; in this case you have a relation to the present and so it's grammatically correct to use the present tense to express an future action.
(bytheway: it's the same with the past tense, but it isn't really used).
It's quite a difference between "Tomorrow we work." and "We work tomorrow." Is there a way to work out the same difference in Italian? Is "Tomorrow we work" then translated to "Lavoriamo domani."? Thus is the meaning of the placement of tomorrow/domani at the end vs. the beginning just the opposite in English and in Italian?