The OED duly lists the sense ‘enclosed field of any size’ as particular to AU and NZ; elsewhere the word refers only to a small enclosure in grass used to pasture horses. It’s a variant of the now-dialectal word parrock, a close relative of park, all originally meaning ‘enclosed place’.
That’s an awesome picture! It’s also great to learn about your parents and childhood. Yeah I’m used to paddock meaning a horse pasture, so I’m glad you clarified. On my farm we grow corn and soybeans. I try to garden every year, but no one wants to weed it.. I live beside a coal mine and they tested for natural gas, but decided it was richer several miles away and set up further north.