And also Kaido spared his life back then in Wano. He couldnt kill Momo by himself, way before Yamato.
Also, he had no hesitation to kill Tama, which he assumed as dead. There was no reaction like that, even tho she must be more or less the same age as Momo.
Additionaly, Momo has exact the DF of Kaido smells to hard like a foreshadowing to me.