Interesting case...well, PR
As much as you don't believe you commited fraud, you did intentional withhold information that your marriage is failing before landing and had every opportunity to withdraw your ex from your PR apllication. But instead you intend to go ahead and land as married so that your ex spouse can get PR that she was not entitled to get. Otherwise why did you wait until AFTER you both land as PR to divorce instead of beforehand.
Anyway, that is in the past and done. However expect your new PR sponsorship for both your new wife and kid to be put under a microscope. They may likely suspect that you and your ex collaborated so both get PR and divorced after landing on purpose with the intention of sponsoring future spouses. They will see that you both got divorced shortly after landing and that is a huge red flag.
Hmmm not sure if this is true (that this is necessarily fraud). A marriage can be falling apart for years but then the couple go for counselling and save it. In fact, it's probably a sign that the marriage is genuine & real, with real problems and challenges and not just an agreement on paper. Now, the situation would be different if they were, say, legally separated (is there such a thing in OP's home country's legal system?).
Of course a divorce following landing immediately is a huge red flag.
Let's look to the other side of things: applications take so long that people's circumstances change significantly. Assuming genuine intents, maybe they decide to stay together for an *INDEFINITE* amount of time (not permanent, just indefinite, as in with no plan to end the marriage) when they land....then it's legit. That means no sponsoring someone though. If OP remarries in Canada then doesn't really matter, no fraud. If OP wants to sponsor someone, it will take something like 5-10 years before they can do that (I have zero info on that, please fact-check). If OP really wants to sponsor the new family....then that's the person they should add to the application.
Sorry to hear of your troubles, OP. I think the bottom line is, you cannot sponsor more than one spouse within the same "frame of time"...you have to choose one. Depending on your circumstances, you probably can add kids from both families....but you have to choose one spouse, with whom to actually live right now.