My brother and sister watched a scary movie?

Ok my dad was in the room and we were watching the recent batman movie the dark knight. My brother and sister are young and I am now afraid that they are going to have nightmares tonight because they saw the end of the movie with gordon and Harvey dent. Is there anything I can do besides letting them sleep in my room tonight? I feel really bad for letting this happen and afterwards I realized that I too was scared from the movie. Please help me