Could you ask her what her favorite author is and send a book (with gift receipt so she can exchange if she already has it?) Or what her favorite type of wine is and send a bottle in your price range? A basket of her favorite fruits? I love gifts like that.
Same for your grandaughter (not the wine, of course) but what books she's in to these days. Things like that.
Gifts that show you know her and love her rather than just expensive, I bet she'd be touched.
Parents-in-Law. What do/did you call them?