I think when Grandchildren are older, and probably earning their own money - if you get no thanks, then time to call it a day. I usually give my two grandchildren money (seems the norm these days) but if they can’t even send a quick text, I would seriously consider whether they value your gift. Stop sending money and in your Christmas cards to them - say you have donated to a charity of your choice. We don’t buy gifts for the adults in our family - just for the teenagers. This Christmas I was surprised to receive a gift (totally unexpected) between the two of them. They had saved their money earnt from their part time jobs but wanted to give me a gift. This meant a lot to me - not the gift but the thoughts behind giving.