Carmilla turned out to be great, easily the best in the anthology. Of the others:
Walpole - The Castle of Otranto: peasant boy turns out to be rightful heir to the [domain of a baron -- what do you call that?]. Supernatural forces make the current baron abdicate.
Reeve - The Old English Baron: see The Castle of Otranto, only it takes forever to end after the climax. Otranto was basically the first Gothic story and this is one of the first thereafter; this apes it pretty closely.
Lewis - Mistrust: No supernatural elements. More psychological, typical lovers-from-warring-houses tale with a heavy-handed theme of Mistrust driving the narrative. Actually pretty good.
Mary Shelley - The Heir of Mondolfo: No supernatural elements. Heir to the baroncy(?) marries a peasant girl and love wins.
I have an eight-year-old nephew I'd like to give a copy of the Scary Stories to Tell in ther Dark omnibus but I'm afraid the pictures would give him nightmares (not to mention he has three younger brothers, but I don't see how I can avoid giving the eldest the book until he's like 16). When I was that age the stories didn't affect me at all but then you have things like this: