Annie Something to bear in mind, perhaps, is that your DGCs may move to anywhere in the world in the future because of jobs or just changing circumstances. Would you prefer to be in your present home or living near your DD should that happen?
I think what I'm trying to say (rather ineptly) is, it's time to do what you feel you'd like to do.
I used to work for an organisation, which specialised in housing the elderly, and it was always upsetting, for applicants and us, when the applicants had acted in the best interests of their children/grandchildren and then realised that it wasn't the best decision after all.
As others have said, it's not your physical presence that they need so much now. They know that you're there for them wherever you and they are.
Staying put may be the right thing, but if that's what you decide, make sure it's for you!