The meaning you wrote is correct. (When used with a specific time reference, the present indicative is more commonly used to express a future action than simple future tense, especially with "coming" and "going" verbs like, andare, venire, partire, arrivare, ecc.) However, even though duolingo seems to expect us to translate "they will go to the store tomorrow" as "vanno all negozio domani" when converting from English to Italian, it usually will not accept the equivalent answer when translating from the opposite direction. So, for a sentence written in present indicative form to express a future action, they want us to translate it as present tense even when it sounds awkward. It's just one of those quirks we have to live with. :-(
"Do you come to the party tomorrow?" is incorrect in English.The present simple tense (as given in the sentence) is not used for future meaning. It should be either "Are you coming to the party tomorrow?"(if it refers to an arrangement or plan) or "Will you come to the party tomorrow?"
The English is awkward and makes answering more complicated because it would not be said like that so it makes you second-guess the answer. It might be how it is in Italian, but it should fit with what makes sense for the native language of the learner, too. 'Are you going to' or 'Will you come to' rather than 'do you come to' makes way more sense. 'Do you come to the party' sounds like some weird conversation happening with a time traveler who has already experienced events and is being asked by someone planning to go to the party. See how awkard?