Yo I've actually been thinking about this. Kaido talks about Whitebeard as if he respects him (when he complains that WB was allowed to go out like he did and Kaido couldnt' die), I don't think he was there to kill WB. I honestly think he was there to save Ace and help him.
Shanks has some "Order" shit going on about him, especially after directly talking to the Gorosei the way he did, I don't for one second believe he's made out to who we think he is. He's not "bad" but I don't think he's that good either. I think he's going to be a super flawed character and we are going to find out that Shanks prevented Kaido from going to help WB out.