Translation:Where are you going over the holidays?
"Where are you going for the holidays?" is wrong apparently, even though "dros" can be translated as "over" or "for".
It said Where do you go for the holidays was wrong and gave me the correction of Where do you go in the holidays. That seems wrong to me.
What you call "vacation" we call "holiday". What you call a "holiday" we call a "festival" (especially in the religious sense - St David's Day is a festival, Easter, Christmas are festivals). Obviously nowadays the word "festival" is more thought of as a music festival. Unfortunately, for our cousins across the pond, Welsh makes no allowances for this and you'll need to use "gwyliau" for "vacation" and "gwyl" for "holidays".
Not really because dros means "over" or "for" and gwyliau is plural "holidays".
Where are you going for the holidays? was correct on other questions so why not here?
Another reason why this is annoying: in another session 'on holiday' was set, I can't remember what I put, not dros, but the right answer given was AR y gwyliau (which I'd assumed was too obvious). If that was indeed right then this should definitely not be translated 'on'.