It is not a straight forward thing when a PR has a baby outside Canada, especially when they don't meet the residency obligation.
If you are set on having the baby outside Canada, your wife would have to apply for a TRV/TRP for him as soon as he is born and she has the birth certificate. A TRV may be refused based on that your intention is for the baby to stay permanently and not to visit. In that case, you can apply for a TRP based on that it would be hardship on your family to be separated and your wife needs to take the baby to Canada in order to sponsor him.
If the TRP is denied as well, you have two options. One is that your wife goes without the baby to Canada in order to sponsor him, the other is that you go without wife and baby to Canada in order to sponsor him. It does not matter that she was originally the principal applicant. Now that you are both PR, your PR is as good as hers and you can sponsor as well. A PR sponsor must reside in Canada so you can not leave during the processing time except for a short vacation at most.
If the baby is granted a TRV, he will be a visitor in Canada and it is possible that he will not be covered by health care in which case you would have to make sure you have emergency/accident insurance for him. You also have to make sure you apply to extend his TRV after 6 months but you can sponsor him outland through your home country visa office and the processing time depends on your country. A PR sponsor must reside in Canada so your wife can not leave during the processing time. If he is granted a TRP, he would be covered by health care but you would not have the option to sponsor him outland any more, you would have to apply inland based on H/C grounds and the processing time for that can be long, I have heard 18 months.
If you/wife do not meet the RO, things get even more complicated because it is possible that the one of you coming to Canada to sponsor gets reported in which case you would have to appeal for your PR using humanitarian grounds of taking care of sick parents. During the appeal processing time, it is unlikely that anything will move very fast with the sponsorship of the baby as they would like to see if you keep your PR first. If you are not reported on entry, immigration will notice in your sponsorship application that you do not meet the RO and will call you in for an interview to explain your situation.
In order to avoid this mess, I would suggest that your wife have the baby in Canada instead.