My parents have set up a trust,so that when the first one dies their half of the estate goes into the trust and cannot be touched by the local council. Only the trustees have control over it - and I'm one of them!
So if the surviving parent then has to go into a nursing home the council can still force a house sale but they only get half the proceeds.
If you try and add other peoples names to the ownership of the house the authorities will see right through it,especially if your parents are elderly.
Equity release is an option,but doesn't really help you with your plans to live there yourself.
I suggest you consult a lawyer and get or parents to update their wills if they have them,or if not,set up their wills asap.
It sounds to me that as your parents are 'very elderly' then you will need to set up a power of attorney aswell.Which is someone who can legally make decisions on your parents behalf should they become incapable themselves.