You will find several useful links here.
First, for seniors, the Government of Canada site, which gives you most of the information you need:
Canada – Changes to your taxes when you turn 65 years old
The same site of the Quebec government:
Québec – Site for seniors
Website of the Office for Handicapped Persons of Quebec:
O.P.H.Q. – Publications in English
And here is the link that gives you information on the tax credit for home support for an elderly person.
Québec – Crédit d’impôts pour maintien à domicile
And the document that helps you obtain the tax credit:
Québec – Formulaire pour crédit d’impôts
Office des Personnes Handicapées du Québec – Fiscal help
O.P.H.Q. – Family support guide