Poster asking for thoughts on writing a letter to the hotel or something else has turned this thread into a plitical forum. All of a sudden you read about the left and right wings, republicans and democrats, etc.
You have to love this freedom that we have.
I say, write a letter but don't get your hopes too high that they will change. It is a hotel in a foreign country that caters to a large client base, with predominance on Europeans. If the children are curious enough, they can get it someplace else... no matter how much supervision and guidance is given. There will always be peer pressure and good old curiosity.