Sorry, never got that far “Children of Dune” was the most I could take.
You’re missing out, after Children of Dune, the story skips forward about 3,000 years to God Emperor of Dune, where Paul’s son Leto II has mostly metamorphosed into a sandworm and has been ruling the known universe for millenia. It’s at this point that Duncan Idaho becomes one of the central figures of the story.