They tell him Kinemon is already going to save Momonosuke so Sanji doesn't need to go there.
Think this is a misdirect, Sanji will still go after Momo. Izou and Kawa will take Zoro to Live Floor but run into Hiyori and leave him with her.
l'm thinking that too. Especially now with Yamato leaving Momo, I feel Kinemon is far too weak to protect Momo. I think Oda wants Sanji to protect the father/adoptive son duo.
Sanji has been only caring about them since the raid started
And his interest in there predicament was set-up since PH.
As of now....I call bullshit on Sanji not going to them eventually. He's only been caring about them since Onigashma part started.
976 -989 = Only cared about Momo
990 -1005 = Only cared about Kinemon
1006 -1012 = Wanted to help both, (chose Momo tho).
Sanji will come in clutch and save both of them from King is what I'm thinking.