I am usually skeptical about books of one reading level adapted for another. In fact, let's be honest--I generally hate them! I feel strongly that adapted books simply rob the reader of the full, satisfying experience of reading the book as it was written, when they are able to understand it. The seven year old who reads the "illustrated, adapted" version of Moby Dick will never take the time to sit down and read the proper version, because they will feel like they already know the book. And of course they don't. However......I love the Moomins. I want so much for the Moomins to find a following here (and I have tried like the dickens to get kids to read the books!) I first read them about a decade ago and was absolutely charmed. Since the Moomins have proven themselves adaptable-Tove Jansson herself wrote about their adventures both as a comic stip and then as a series of chapter books. So perhaps, in the right hands, with the original artwork intact, they can be made relevent to young listeners who will then want to revisit them when they can read the books themselves.
If you want to be one step ahead of this oncoming Finnish invasion, I suggest you go to your local library and check out the Moomintrolls for yourself. Then you'll be ready for any potential trips to Moomin World , the official Moomin theme park (should Disney World prove too cliche for a family vacation!)