"Your parents are going to miss you."
Translation:Dina föräldrar kommer att sakna dig.
ska involves someone controlling the action in a way that just doesn't work well with this sentence. The English sentence here is just a prediction, you're talking about something that will probably happen. For those cases, it's always kommer att in Swedish.
In that case, I think that the English translation should definitely be: "Your parents will miss you." Then there won't be any confusion here.