M.D.
Daily letters are a bit, but I do understand he just wants to be part of his grandchildren's life. that every day he's thinking of his grandchildren, is that really wrong? Seeing them every month, is that really wrong? buying them gifts? My parents are very close to my kids. I had the first boy in the family and my dad has a very close tie with my oldest son. I LOVE IT! The other day, my dad was upset because my son doesn't talk to him like he did when he was a little boy, he said, I tried to asked him questions how his trip was, but all I got was "fine". Both my grandpa's are still alive, and I LOVE seeing them, although it's not too often, since I live in Texas and they live in Illinois. I only have one of my grandmas. I remember spending time with them, dressing up, having tea parties when I was little. No one can take those memories from me.
I do understand boundaries, but what you've wrote, I don't think there is anything wrong with what grandpa wants. Hopefully, everyone can come to a better respect for each other.