Wouldn't 'Have you any plans for the weekend?' also be a correct translation?
I did the same thing and they marked me wrong. "Have you any plans....." is more polite.
Added that now. The course was built without support for the "have you?" construction initially, so it's missing in quite a few places since I need to add it manually everywhere.
I will note, though, that this phrasing is only more polite in some places where it actually exists. Large parts of the English-speaking world doesn't even consider it grammatical.
I wonder why this in the politics section? Maybe because politicians like long, long weekends?