We have been several times, we stay at a small campsite about 10 minutes away (Au Bois du Cey )and spend 2 days there as its such a good day out and we often want to see the shows more than once. You can get the translation head sets but they are not totally necessary as you can get the drift of the stories from the acting.
They have different timings of shows each day so make sure you pick up a programme on your way and plan your day round the show times. Be prepared to do quite a bit of walking and get to the individual shows early to get good seats.
All the shows are spectacular, although the indoor show the musketeers is a bit bizarre and if you are allergic to horses like me take your antihistmines.
If you wanted to see the night time show (Cinescenie) its not on every night so check before you go. Its in a different part of the park so you will have to buy separate tickets.
Also queues from the carpark are massive for the night time shows as everyone is leaving at the same time so you will neeed to factor that into your travel time.- Thats one of the reasons we stay close by. They recently opened a roman themed hotel on the site but dont know how much it costs to stay there.
They also do a evening battle of the donjon show with fireworks which is good its an extra though and you have to pay an additioal charge or it but - there is a themed meal and show -called battle of the drap d'or which if you book for the later sitting you can then stay on for the donjon evening show for a small additional cost.
Its totally fab and really well worth a trip.