Alright let's talk Big Mom.
Right now, there are two places she could go. She could arrive at Cacao Island, not realizing that the Strawhats have already left, and get involved in what's happening there. Or, she could skip Cacao and arrive straight towards the Sunny (which could easily be explained by Perospero getting a call along the lines of "They left in X direction Y minutes ago!").
If she heads straight for the Sunny: Some sort of fight is going to break out. But Strawhats can't beat her, otherwise Wano would lose all of it's tension. But I can't think of any reasonable third-party that could rescue them (Granted, it's not impossible for CP0 or Pudding to fly in, but that would be dumb. Still, after this chapter, no dumb possibility is impossible), or any way that they could talk their way out of things (Even if she believes that Sanji helped with the cake, they can't say anything to make up for the Mother Carmel photo). So I'm going to say that this is the less likely possibility.
If she heads to Cacao: She would have to either stay and get caught up in the fight with Germa/Fishman, or leave and head straight for Luffy. If she stays to fight, the other side is pretty much dead, so that probably won't happen. But if she leaves right away, we'd just get a situation similar to the first one, which wouldn't work either. So something would have to happen on Cacao to her before she leaves to chase the Sunny, or attempts to join in the battle.
The most likely thing would be meeting up with Pudding, where she learns the truth about Sanji baking the Cake. After she find out about it, who knows. What I do know is that during the cake musical, Oda established a clear connection between the cake and her memories of Carmel (cake –> taste of croquembouche --> fateful birthday). Her learning the truth about one will lead to the truth about the other.