I like the rental house/cottage idea, too. England, Ireland, Wales or Scotland would seem good bets - esp. with respect to the golfing. On the mainland, perhaps somewhere in the south of France, Spain or Portugal. There are several popular holiday resorts which are effectively English outposts, if Grandma and her beau want something fairly comfy, where they can chat easily with the neighbours. You could use their place as a base for explorations further afield, too. But if Grandma's paying, I wouldn't ditch her altogether - scope out some daytrips that you think she will also enjoy that you can do together. It's always fun seeing a place through someone else's eyes, and it's really a great experience for both of you to share. But it sounds like Gran doesn't need you around all the time, let her and her beau have some romance too.
Best bet, ask her what she wants to do - I know of one quiet, retiring, older woman who had always dreamed of Italy, she finally made it there in her 60s and had the time of her life. My aunt (neither quiet or retiring, I grant you), up and took herself to India to celebrate her 60th birthday.
Who knows what adventures lurk in the hearts of grandmas?
:tumbleweed: