It doesn't matter, because mark my words, my friends, this is great stuff. This record is so well-made, it would seemingly belittle it to classify it as a children's record. However, to be fair, it comes from an era where solid entertainment could be made for kids without feeling the need to completely dumb everything down to levels of absurdity.
Featuring a delightfully over-the-top performance by the great Basil Rathbone, as well as the also-great Peter Fernandez (whose name should be familiar to you from Speed Racer, let alone the great American dubs of Godzilla/Toho movies done at Titra/Titan studios), this is a top-notch effort that will impress you. It even stays overwhelmingly faithful to the book, although simplifying the plot (also there is one minor change that surprised me--without spoiling the story, it has to do with the proof that the group brings back from the Lost World) somewhat, which is obviously required when you reduce a novel to a 38-minute audio story. The script, sound effects, and performances are all enthralling. Even when brief educational factoids are thrown in about a specific dinosaur, it doesn't hinder the plot (if you can believe that)! I enjoyed it immensely, and I think any kaiju and/or dinosaur fan will too!