Well I think it depends on your family. Do you think they have a charity set up at all? Was your grandfather living in a home or cared for by hospice? If so I would probably suggest giving a donation to something like that instead of flowers. Flowers can be very expensive and with the passing of someone elderly, I think your money can be better appreciated in a different way. Edible arrangements are VERY tasty, don't know if you've had one and it could be a cute gesture if your grandmother or other relative is having a reception at their home following the service. If that's the case, I would call and tell the person ahead of time to expect it b/c it will need to be refrigerated and such. I'm sorry for your loss.