I would dispute at least "The Name of the Rose", I'd say it's just a multi layered story.

A good portion of the book are philosophical discussions, which would be IMHO very boring and not understandable for small children.

The magic of novels like Svejk or Little Prince is that those extra layers are mostly implied, emergent, they're not written out explicitly and thus don't bore out the young readers.

This one is a little difficult: the book is laden with multilingual dialogue and notes apparatus; it's not for everybody. That said, I first read The Name of the Rose when I was 11 or 12, and I thoroughly enjoyed it.

Personal anecdote - I rather enjoyed reading "Name of the rose" as a kid. I don't remember how old I was at the time, maybe somewhere around 11-13. While I obviously didn't understand a lot of the details at the time, I remember vaguely feeling that there was something deeper than just a murder plot. All in all, it was a pretty good experience, and served as my gateway drug into other books by Eco.