I remember an animated cartoon movie (American I think), in the early 2000's about a group of children (8-12 yo), who are in an abandoned amusement park.
In the beginning, the place is cool, they have fun. But in the end, it's like a nightmare park, the children are pursued by monsters or other strange things ... And I think that one of the heroes died ... And another was made and loved this scary-place ...
This was not very well drawn, in the style of the Jumanji cartoon :
... I watched it when I was a child, on a movie-theater ; that's all that I can remember about it.