Was it them at the end? *mild spoilers*

From the ending I got that they were unable to ecsape and that in the end they ended up living in the fairytale hence the book. So they were like the characters in that book never really being able to escape from the forest.

The Note Book is the key to their world that they have created with the power of their minds! Another fact is that in the real world it also X-Mas, like it always is in theirs! The Note Book is empty except for the last page with the drawing of the three childeren! Somehow they can leave their world due to the Note Book and come to the real world! Normally they should look old, their age in the real world, but probably they have mastered their kraft after more than 5O years so good that they can keep their ideal self even in the real world! In short they have become dimension hoppers i.c. from their dimension into ours and back!

Hm, I don't think they have become hoppers or something like that. It's just as the Santa Claus has told them, that on Christmas Eve all their wishes would come true. For them intheir world, in their house it's Christmas every day. And on that special day when in our world there is also Christmas they are able to cross that line. Otherwise there wouldn't be any sense in the time of the year the ending of the film is set.
I think that their visit and the notebook are like a sign that they haven't given up hope, that he has showed them that there are still grown ups that can be trusted. On the other hand the image in the note book isn't showing him but the three kids alone. To me it looks like they want to show him that they are alright and that he dowsn't have to worry. I mean it's clear that although he had to leave their house (because of his own family) he really cared for the children. So to me it wasn't the ultimate positive ending but... you got the idea that the children now have found a tiny bit of their own peace.

I saw this for the first time last night. I didn't recognize those steps from any earlier shots, so I wondered if this was the city, the real world. I don't know why they would be happy, as they are on the last page of the book, if they had not escaped, if all they could do was trap people to take care of them, over and over.