Hopefully based on the responses above everything is clear now that to meet the residency obligation you both , you and your spouse need to return in next few weeks and even then at this stage you may be directed for an interview in secondary given you are borderline with the residency obligation.The PR cards being valid simply means that you can as PRs board a plane back to Canada nothing else.
Even though when you originally applied for PR your spouse was classified as a dependant , once landed she would be responsible for her own residency obligation/PR status so she cannot wait 3 months without risking her status being revoked on entry.
The only positive thing is that your child being an Australian citizen only needs a passport and an ETA to travel to Canada, no visa required to enter on visitor status, although you all would require something extra to transit the US if that is the chosen route.
