this show is really good! its better than goosebumps, which was just really cheesy and weird.
positive messages: the kids work hard to defeat whatever is scaring them, and they occasionally team up with other characters to defeat them.
violence: not really an issue, although i guess scary stuff could technically be an issue. in one recent episode, "dreamcatcher," the bogeyman is FREAKY. the face of a clown with the body of a spider and ghost. O_o some other elements in the show are scary, for example, a doll that comes to life and tries to get rid of its little girl owner.
sexuality: not really a concern either, although some girl characters wear skimpy outfits. in "creature feature," when a girl character is lying down on a laboratory stretcher, you can see cleavage. again, in "dreamcatcher," there is a really quick zoomed up glimpse down a girl's shirt (no nudity).
other than that it's a great show and great family time. my dad likes the show too!