Can someone help find a movie title, please?

Its above a teenage boy and friends following a treasure map against family’s wishes that takes them on several adventures, that lead them to his Grandfather, Jesse James who they thought was dead. He’s being followed by bully from school. One scene they find Jesse’s underground hideout. They may have found a clue on an old train. Set possibly in late 1890’s to early 1900’s. Its adventure, comedy