Writing Test

Question

I was supposed to translate, "this year, on the 24th of December, I am going to cook Christmas Eve Dinner." I translated the latter part of that sentence to "je cuisinerai le repas du Réveillon," which was not accepted. The correct answer was "je vais cuisiner le repas...". However, there was nothing in the quiz so far to indicate that this was to be done in the near future. Was my answer technically correct, or am I missing something?
Thank you

Maarten Kamp · Accepted Answer

Benjamin, 
your sentence is not grammatically wrong. 
However, the usual translation of the English expression ‘.. ( to be ) going to do something ‘ into French is with the future proche ‘ .. aller faire qqc ‘. 
The French future simple tense is usually used when the English expression is  ‘… will do something ‘
Additionally, if the question was associated with the lesson you linked, the expected response will be future proche as that is the focus of the lesson.
Le Futur Proche (Indicatif)
Futur