Anita,

Letters are often unappreciated in this age, which is sad. I gave my mother a letter a few times and, like you it was either ignored or not appreciated. I do not know his view of letters so maybe he would not understand.
I know a lot of his interests, and maybe I can indirectly communicate to him and slide it into a conversation. It might be hard and take time, but I think that is a great idea to ease the subject without being forceful!