Just use email...
My Mom (70s, retired special ed teacher) got the family on Signal and it's a breeze to do video calls or send pictures/messages to people.
They occasionally have a donation popup but it's one of the easiest and least intrusive programs I've ever used, and it just works.
This is a brilliant take. I was talking to friends the other day and we were reminiscing about the old days where you'd email and phone people. And if there was a family event you'd shove a quite write up and some photos on your personal web site and email the links out to people. Some parts of the family would mail a newsletter around periodically.
We decided to do the same again.