I worked in the Recreation Dept in a nursing home for several years, and I noticed that many of the ladies enjoyed having baby dolls with changes of clothes. If your grandmother is more of a sentimental type as opposed to an intellectual type, she may like this. The staff makes a big deal when they see the dolls on the ladies' beds or in their arms, so it opens a new avenue of conversation. It also gets them talking about their children/grandchildren/greatgrandchildren, and conversation is always great, especially when one is depressed. You can regularly send doll clothes to match the seasons and holidays.
If you think this is a good idea, and your grandmother still has normal mental capabilities (meaning no dementia), tell her you're sending the doll and clothes to remind her of her of when her children were babies, this way she won't think you're treating her like a little girl. If she has dementia, then she she most likely won't feel that way and just feel like she has someyhing to "take care of".
If she's the intellectual type, but has trouble seeing/hearing, how about something tactile, like Playdough, and ask her to try her hand at sculpting, and her artwork can be displayed throughout the home. Explain to her that nothing grand is expected of her, to just give it a shot, and to let her memories be her guide. Suggest she start out with flowers, as they are easiest for beginners. Send her some disposable cameras with stamped return envelopes so that the staff can take pictures of her work and mail the cameras back to you for processing. You can make a big deal out of it when you speak to her, telling her you've framed the photos and have them displayed in your home for all to enjoy.
How's that for a start? Sound like something she'd go for?