Depending on the profile of your parents: ties to return, travel history, medical issues, personal funds (not yours). And of course you need to be eligible to be a host for super visa applicants.
If the profile is strong, you can try for a tourist visa. If not. you would better opt for super visa
If you don't have any family ties, there's no way to strengthen that. Try to strengthen your other strengths like ties to return, purpose of visit, funds, etc.
GCMS is always a good idea.
You won't get any refund in this case.
Talk to an immigration consultant or a lawyer. Your assumptions are groundless and knowledge is very superficial or generated by AI, you are not eligible for PRRA.
It's done automatically for many years already but you are right, no issue in this case if there are small discrepancies.
Also you can ATIP your PR application to get all the information you need.
Yes, you need to meet minimum necessary income requirements. You spouse can cosign it to meet that.
So he is not a tie either as he is not a dependant.
How old is the elder son?
Grandsons and parents are not the ties.
Property, job, etc? Country of residence?
If she needs a longer stay and her profile is quite weak, she would better consider a super visa if you qualify (you are a PR or a citizen).
If not, shorter stay, 2-3 weeks tops with...
The issue with the duration mentioned for stay : for 3 months she would have needed to show some huge amount of funds.
And a baby’s delivery and support is not really consistent with a temporary stay.