There should be lots of ideas if you look at a shop for blind people.
$1.
You can probably find all these items in other countries.
A watch he can use, either tactile or talking, would help him keep track of the time and days of the week.
An accessible radio would give him topical and novel content to listen to, Radio 4 in the UK or, I guess, NPR in the USA.
If you don't know about it, the
$1 standard for talking books and players could be of interest.
Helping him be independently mobile would also be important, so having a cane and being trained to use could be useful to him.
Similarly having an accessible mobile phone will help him keep in touch with friends and family.
Gardening may also be a hobby still open to him.
I'm guessing that at 88 the computer revolution has passed him by.
You don't says if grandfather has no vision at all or is partially sighted.