The Return of the Third-Grade Ghosthunters: A Ghost on the Farm? (Third-Grade Ghosthunters #3) by Grace Maccarone

Meet after dinner.
Ghost business.
Very important.

"Owowowoooo. . .owowowooooo. . ."
Then Chuck saw it. . .in the far corner of the room. . .the ghost wolf!   Shiny eyes. . .hanging tongue. . .sharp teeth. . . .

Something is haunting the third grade's class trip. And it's up to the third-grade ghosthunters to find out what it is!