To be entirely honest I haven't set up a shared Google calendar bc I don't particularly want to set myself up to be responsible for making sure I enter everything.
I note all appts for myself. He has been told to give the school his address repeatedly to get notices. I remind him to do that still since he hasn't.
I can see a Google calendar turning into "well now you forgot to add something WTBH & I missed it and its your fault".
My experience is that any attempts I make get used against me and I have been worried about that.