I thought the chapter made it pretty clear that Brook, Chopper and Nami were going with Luffy to get Sanji. They were kind of neglected at the end of the Dressrosa arc so it does kind of make sense I guess. Seems like the rest of the crew will go to Wano unless something else splits them up further in the upcoming chapter.
And yeah, him hearing the elephant isn't surprising. He was able to hear the Sea Kings on Mermaid Island (like Gol D. Roger) so chalk it up to it being because he either is a D or because of his conqueror's haki. Or maybe some unknown third reason, who knows.
For clarity's sake, Luffy+co going for Sanji, Nekomushi+co going for Marco and Kinemon+co are going to Wano. Don't know who's joining Nekomushi at this point though, whether it's other Strawhats, the Heart Pirates or just some Minks.