Kaido having a son might explain why he chose not kill to directly kill Momo. The fact that Momo didn't have any person dreams or aspirations is probably how Kaido's son was back then as well. Hell, they're probably even around the same age (28).
His son will be a crybaby, just like his father. He will have "some fun" with Kaido's hostage but who knows? Luffy and friends might kidnap this Kiddo as hostage, to payback for what Kaido did against Oden.