Tommy - thanks so much for your help - I finally got it to work!
Not exactly what you wrote, but once got clued in to the need for the id (somehow I thought that was always available as the PK of the record in AR) i was able to figure it out…
I come into this having worked with php for years, but doing just some OOP (mostly database libraries and sanitizing input) and am an MVC / frameworks / Yii virgin… I am really enjoying this but it takes a bit to get my 60 year-old head around this all at once!!
Now I think i will try to abstract actionUpdateAjax a bit further so I can feed it other variables.