Based on the current IRCC updates, a super visa stay of up to 2 years is possible only on the initial visit. If your parents are granted super visas but they decide to stay for just 6-12 months then the one-time opportunity to stay for up to 2 years would be lost.
Do state a visit of at least 8-10 months otherwise there's a possibility that their applications could be considered for regular TRVs if a 6 months' visit is stated.
You must prove you meet LICO for yourself + your wife + your three children + your parents + your mother-in-law (if she was invited on a super visa) + your dad-in-law (if you had applied for a super visa for him).
LICO for 8 persons if your dad-in-law was not invited for a super visa, or
LICO for 9 persons if your dad-in-law was invited for a super visa
That said, if your/the combined incomes of your wife and yourself do not meet LICO then I would recommend you do not apply for super visas for your parents.
In addition to LICO, you would need to include other financial evidence to prove you can support your parents' stay such as financial investments, pension funds, bank statements, employment letter(s), etc.
1. Is your mom and dad entitled to any other post-retirement benefits?
2. Do your parents need to return home to renew their pension each year?
3. When does your mom's pension likely to begin?
Is it a residential property or land?
Does he earn any income from this property?
Do they have a mortgage?
You can extend support to the point of accommodation and maybe offering to pay for their airfare. Your parents must prove they won't be too financially dependent on you. That said, if they are able to prove they have other strong reasons to return home then their slightly inadequate financial situation might not affect the visa decisions.
Yes, it is true. All going well, if your parents are granted TRVs + if the officer at the POE allows them to stay for up to 6 months, your parents can apply to extend their stay.
Other points:
1. Regardless of a TRV or a super visa, the purpose of your parents' visit must not be to take care of your wife or your newborn baby.
2. Do your parents live with other dependents (your unmarried siblings, your grandparents)?
3. Do they have a lease/rent agreement for the place where they live? Or do they own that property?
4. Do your parents volunteer for any social, religious or other causes?