I'm thinking of leaving my grandparents care to their 4 daughters
Do you not care about your grandparents?
They do not keep me happy, I try keeping sane but they are becoming more and more of a pain in my ass.
It's hard to take care of the elderly but if you can help then you should do so. You shouldn't rely on other people to take the initiative. They will appreciate you more for helping.
All I want is 100% of the property and some small legal protection. That should be a decent request.
I'm sorry you are thinking that way. You shouldn't try and put all the responsibility on other people. You should work out some kind of schedule so that everyone is helping.