I remember a book I read in school, the year was about 1986 or 87 and the book was a about a little boy getting invited to a Halloween costume party. When he gets there he realizes that the other kids there were not dressed up as ghost or skeletons, but were actually ghosts and things. It was not a scary book and the they all start dancing and singing.

I have been trying to remember this book for years and would like to get a copy if i can for my son if I can actually remember the title. Any help would be great thanks.