Don't forget crossword puzzles! I like the little books with 50 NY Times puzzles. You can get easy, difficult and a mix of both to fit your mood.
Playing card games is also good brain exercise - as well as being fun and companionable.
And then, if you are lucky and one of your grand children - or a niece or nephew - likes to hear family stories, you can dredge out and dust off your memories of all the old family stories you were told when you were young, and add to them your own childhood escapades. If you find the right young listener, you will be asked to tell the same stories again and again.
Good point to bring up, Zucchiniflower.

Thank you,

birte

OOps, I certainly am observant.... several days later and I finally discover that it was you, CTena Louise,( or LavenderLuv) who brought up the subject and not Zucchiniflower.......sorry - passed me by completely till this moment. I'd better play scrabble or read some Shakespeare, my brain must need more flexing than it is getting.