There was a film I used to watch as a kid where a group of children I think went to stay at their grandmas and then when they were at a carnival they found a haunted house. I also remember something about a women losing a necklace im the woods or something
Could it be “The Watcher in the Woods”?
http://www.imdb.com/title/tt0081738/?ref_=nv_sr_1
Some elements of your description match.
“The Ghost Club”(2003)
Trailer: https://www.youtube.com/watch?v=S35j94nkPqM