Vincent Price Saves It! (Well, maybe mostly.) Minor SPOILERS
To explain just why House on Haunted Hill from 1959 is so bad, some SPOILERS may be necessary. I will try to make them as minor as possible. I think my main problem with this movie is I came in with hopes set much too high, probably expecting something resembling a fairly good to great haunted house movie along the lines of The Haunting from 1963, which is unfair as The Haunting was based on what must have been a very good book and House on Haunted Hill is based on a sadly crummy screenplay. I also expected that because the movie was so popular in its day it must be on some level good as it is now considered a classic. I made the same mistake with The Rocky Horror Picture Show, coming out of that feeling there was something wrong with me for hating it so much. (I didn't hate House on Haunted Hill that much.)
All three films follow the convention of "the old dark house," with a bunch of people invited to a gathering in a supposedly haunted mansion. The house in House on Haunted Hill has a backstory featuring seven murders. Let me first say how much I absolutely hate the house featured in House on Haunted Hill. I learned it is a very famous mansion designed by Frank Lloyd Wright. It is a cement block monstrosity probably meant to resemble an Egyptian or Aztec temple and is totally wrong for the gothic style of this type of story. The interiors are quite a bit better, between acceptable and good, and much more in line with the conventions of "the old dark house." The cast and their performances range from adequate to great. If this movie is worth watching at all it is for Vincent Price who is so cool and brilliant. I have liked Richard Long ever since I was a small child and found him to be good in this. Carolyn Craig as Nora Manning is very beautiful and called upon to scream a lot to the point of annoying some viewers. I must say hers are some of the better screams in movies of this type and it's a wonder she had any speaking voice left.
Where the film totally falls apart is the plot. It starts out to be a possible haunted house picture where skeptics become believers, then tries the Scooby-Doo approach of having a logical explanation, only there were probably Scooby-Doo episodes better thought out than this. A few occurrences which couldn't have been faked might be explained as hysteria on the part of Nora, but not all the inexplicable aspects can fit this description. Neither does it work as a story where there is a fake haunting overshadowed by a real haunting. It is also a murder mystery. It's pretty darn obvious that the murderer isn't the one to whom all fingers are pointed because it's always someone you don't suspect. When the actual situation is revealed it comes as a somewhat surprising twist, at least I didn't figure it out but then I wasn't trying that hard. In the end it is a half-baked premise which raises way more questions than it answers and is extremely disappointing. If you were expecting either a genuinely scary movie or a well-written story, I would recommend The Haunting for starters. If you want a crappy excuse for cheating the audience, try Mark of the Vampire. This falls somewhere in between. It's really annoying.
On the plus side, those other films don't have the incomparable Vincent Price. If you're a fan or even casually like him, it's worth watching for his performance alone, and as I said the rest of the cast is good too.
As for whether the movie is suitable for kids, it is rated 16+ on Amazon's streaming platform, for alcohol and tobacco use and scary situations. (There are a few startling scenes but they're not that scary.) Doubtless many kids in the 1959 audience were younger than 16 but American youth has wimped out since then, or the adults have in their ideas of what kids can handle. It does feature a couple of deaths. I think the main danger to kids from this film would be boredom and disappointment. It's not "so bad it's good." If you want laugh out loud horror watch Troll 2. If House on Haunted Hill is laughable either intentionally or unintentionally it was lost on me; I didn't find it amusing at all but it has some entertainment value mainly thanks to Vincent Price.