Translation:Are the parents sleeping in the hotel?
And yet "Are the parents in the hotel sleeping?" can have a different meaning to "Are the parents sleeping in the hotel?". The former questions if they are sleeping there now, whereas the later could be asking the same or it could be asking if that's where they are sleeping when they do sleep.
That order is also correct, but it is less common I think and I would say it is less 'nice'.
In general people will understand you if your word order isn't completely correct. So if you're a beginner you'll get away with some mistakes. But it starts being annoying if you're more advanced. You can compare it to saying We go tomorrow to the hotel in English. It's not the end of the world, but it's better to try to get it right. :)