My daughter thinks I am horrible. I absolutly hate doing mail. I never send cards even if I go out of my way and buy them. when my daughter told me she would really like to get cards from me every now and then I really tried but it just didn't last. I stink at it!!!
At my child care center we studied post offices for a week in February a few years ago. I told each of my parents to tell their family members to send the kids cards and we would put them in their new mailboxes in their cubbies. I got several cards every day for quite a while after that. maybe if you make up a story like this and tell the grandparents they would not be offended and think they were really doing a cool thing. But then again, they may be just like me and hate doing the whole mail thing. Either way, the kids need to know it's not them. You just give them a hug and tell them it's from the grand parents, they love them but just don't send cards and stuff.