Hi,
Would her coming alone (Option 1) be the best option then if she can manage to have her husabnd take care of the kids, all under 12. Or would it seem suspicious or irresponsible?
Visa or not, it would seem rather careless/inhumane to leave a newborn baby without his/her mother for 3 weeks. However, if she intends to apply next summer then the baby would be older/someone else can take care of him/her.
My suggestions:
1. Her TRV application will depend on your financials which unfortunately are not strong at the moment. You must try and save up some more before you apply for her.
2. Do keep her visit to 2-2.5 weeks max. You must draw up a detailed day-by-day itinerary for sightseeing, your convocation, seeing how you live/work, meeting friends/family, etc with expense estimates and prove that you (ideally your mom) can afford it + airfare.
3. Notarizing the invitation letter is not necessary. Do check with the VAC for her country.
4. Her documents would include:
a. Marriage certificate + birth certificates of all her children + any government issued proofs that everyone stay at the same address
b. Rent agreement + 2-3 rent receipts (although this is not a reason to return because her husband earns/pays the rent)
c. Evidence that the school-going children have enrolled for the next academic year (tuition fee receipts, etc)
d. She must focus on her family ties as that's her only strong tie. Do prepare an explanation 'My strong ties: Family (For her immediate family members: Name/Age/Nationality/Relationship/Address + Extended Family (broadly, for example, 'Both my brothers and their families live in the same city + one maternal cousin and her family live in the same city, etc. Names and details are not required)
e. I suggest she must include her name as a joint account holder for the bank account even if the balance is low. Can they save a bit more by next summer?
f. Apart from her kids, can your mom also prove 1-2 other compelling reasons to return home by a specific date with evidence? For example, wedding in the immediate family, or surgery scheduled for one of the grandparents, etc?
g. Now the key advice: Your invitation letter is most critical. I recommend you make the tone of the letter a bit emotional.... you could mention that your mom made several sacrifices to raise you/your siblings (if any) with good values + to ensure you received good education, etc etc.... and how much it would mean to you to have your mom at your convocation, a proud achievement in your life, also to show her how you live and work in Canada, etc etc.... and this little holiday is a token of deep appreciation, gratitude and a gift to your mom from you, etc
Cheers